U.S. patent application number 10/458211 was filed with the patent office on 2003-12-18 for portable drag compressor powered mechanical ventilator.
Invention is credited to Cegielski, Michael J., DeVries, Douglas F., Graves, Warner V. JR., Holmes, Michael B., Williams, Malcolm R..
Application Number | 20030230307 10/458211 |
Document ID | / |
Family ID | 39737655 |
Filed Date | 2003-12-18 |
United States Patent
Application |
20030230307 |
Kind Code |
A1 |
DeVries, Douglas F. ; et
al. |
December 18, 2003 |
Portable drag compressor powered mechanical ventilator
Abstract
A ventilator device and system comprising a rotating compressor,
preferably a drag compressor, which, at the beginning of each
inspiratory ventilation phase, is accelerated to a sufficient speed
to deliver the desired inspiratory gas flow, and is subsequently
stopped or decelerated to a basal flow level to permit the
expiratory ventilation phase to occur. The ventilator device is
small and light weight enough to be utilized in portable
applications. The ventilator device is power efficient enough to
operate for extended periods of time on internal or external
batteries. Also provided is an oxygen blending apparatus which
utilizes solenoid valves having specific orifice sizes for blending
desired amounts of oxygen into the inspiratory gas flow. Also
provided is an exhalation valve having an exhalation flow
transducer which incorporates a radio frequency data base to
provide an attendant controller with specific calibration
information for the exhalation flow transducer.
Inventors: |
DeVries, Douglas F.;
(Yucaipa, CA) ; Cegielski, Michael J.; (Norco,
CA) ; Graves, Warner V. JR.; (Hemet, CA) ;
Williams, Malcolm R.; (San Clemente, CA) ; Holmes,
Michael B.; (Riverside, CA) |
Correspondence
Address: |
Kit M. Stetina
STETINA BRUNDA GARRED & BRUCKER
Suite 250
75 Enterprise
Aliso Viejo
CA
92656
US
|
Family ID: |
39737655 |
Appl. No.: |
10/458211 |
Filed: |
June 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10458211 |
Jun 10, 2003 |
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09050555 |
Mar 30, 1998 |
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Current U.S.
Class: |
128/204.18 |
Current CPC
Class: |
A61M 16/0051 20130101;
A61M 16/0057 20130101; A61M 2016/0039 20130101; A61M 16/206
20140204; A61M 2205/3592 20130101; A61M 2205/42 20130101; A61M
2205/587 20130101; A61M 16/208 20130101; A61M 16/024 20170801; A61M
2016/0021 20130101; A61M 2205/3365 20130101; A61M 16/205 20140204;
A61M 2205/3569 20130101; A61M 2205/3561 20130101; A61M 16/1015
20140204; G01F 1/42 20130101; A61M 16/202 20140204; A61M 16/0833
20140204; A61M 16/107 20140204; A61M 2205/3331 20130101; A61M
2205/581 20130101; A61M 2016/0027 20130101; A61M 16/0069 20140204;
A61M 2205/70 20130101; A61M 16/20 20130101; A61M 2230/46 20130101;
A61M 2205/8206 20130101; A61M 2205/16 20130101; A61M 16/125
20140204; A61M 2205/8212 20130101; A61M 2202/0208 20130101; A61M
2205/502 20130101; A61M 2205/18 20130101; A61M 16/0063 20140204;
G01F 1/40 20130101; A61M 16/12 20130101; A61M 2016/0042 20130101;
A61M 2016/0036 20130101; A61M 16/209 20140204 |
Class at
Publication: |
128/204.18 |
International
Class: |
A61M 016/00 |
Claims
What is claimed is:
1. A rotary drag compressor ventilator device for ventilating the
lungs of a mammalian patient, said device comprising: A. a rotary
drag compressor comprising: i. a housing having a gas inflow
passageway and a gas outflow passageway; ii. a rotor mounted within
said housing, said rotor having a multiplicity of blades formed
circularly therearound such that, when said rotor is rotated in a
first direction, said blades will compress gas within said housing
and expel said compressed gas out of said outflow passageway; iii.
a motor coupled to said compressor for rotating said rotor within
said compressor housing; and B. a controller apparatus to
intermittently accelerate and decelerate the rotation of said rotor
so as to deliver discrete periods of inspiratory gas flow through
said outflow passageway.
2. The ventilator of claim 1, further in combination with: C. an
oxygen blending apparatus connected to said inflow passageway for
blending oxygen with ambient air to provide oxygen-enriched air to
the inlet aperture of said compressor housing.
3. The ventilator of claim 2 wherein said oxygen blending apparatus
comprises: an ambient air receiving passageway; an oxygen receiving
passageway; an accumulator for receiving ambient air through said
ambient air passageway and oxygen through said oxygen passageway;
and, a series of independently actuatable solenoid valves
positioned, in parallel, within the oxygen receiving passageway of
said bending apparatus, each of said solenoid valves having a
predetermined flow rate when fully open, each of said solenoid
valves thereby permitting passage therethrough of a predetermined
amount of oxygen per time period; and, said oxygen blending
apparatus being connected to said controller and said controller
being further programmable to receive input of a desired oxygen
concentration setting and to emit control signals to the solenoid
valves to cause individual opening and closing of said solenoid
valves to result in said desired oxygen concentration within said
accumulator.
4. The ventilator system of claim 3 wherein said solenoid valves
comprises three to five separate solenoid valves.
5. The ventilator system of claim 3 wherein said controller is
programmed to apply a pulse-width modulation signal to control the
opening and closing of said solenoid valves.
6. The ventilator of claim 1 wherein said controller comprises at
least one microprocessor.
7. The ventilator of claim 1 wherein said compressor rotor
comprises a dual-faced compressor rotor having first and second
series of blades mounted opposite sides thereof; and, wherein said
compressor housing is configured to define first and second
compressor flow paths which are positioned in relation to said
first and second series of blades, respectively, such that rotation
of said compressor rotor in said first direction will a) draw gas
into said inflow passageway, b) concomitantly compress and move gas
through both of said first and second flow paths and, c) expel the
combined gas from said first and second compressor flow paths to
compressor flow paths to provide inspiratory gas flow from said
ventilator device.
8. The ventilator of claim 7 wherein said compressor rotor is round
in configuration and has a diameter of 2-6 inches.
9. The ventilator of claim 7 wherein said blades are disposed at
angles of attack of 30-60 degrees.
10. The ventilator of claim 9 wherein said blades are disposed at
55.degree. angles of attack.
11. The compressor of claim 7 wherein said blades are mounted
within concave annular troughs formed on opposite sides of said
dual-faced compressor rotor and wherein said first and second
compressor flow paths are formed in relation to said first and
second annular troughs such that the series of blades mounted
within the first annular trough will compress gas within said first
compressor flow path and the series of blades mounted within said
second trough will compress gas within said second compressor flow
path.
12. The ventilator of claim 7 wherein rotor, including said blades,
had a mass of less than 40 grams.
13. The ventilator of claim 7 wherein said rotor further comprises:
the convex rotor hub having a central transverse motor shaft
receiving aperture formed therein, to facilitate rotation of said
rotor by said motor.
14. The ventilator of claim 7 wherein said rotor is formed of
molded material.
15. The ventilator of claim 7 wherein said blades are formed of
aluminum.
16. The ventilator of claim 7 wherein approximately 30-40 blades
are positioned on either side of said rotor.
17. The ventilator of claim 1 further comprising: a differential
pressure transducer for measuring the difference in pressure
between gas entering the inlet of said compressor and gas exiting
the outlet of said compressor.
18. The ventilator of claim 1 further comprising: a tachometer for
measuring the rotational speed of said compressor.
19. The ventilator of claim 18 wherein said tachometer comprises an
optical encoder.
20. The ventilator of claim 1 further comprising: a differential
pressure transducer for measuring the difference in pressure
between gas entering the inlet of said compressor and gas entering
the outlet of said compressor; a tachometer for measuring the
rotational speed of said compressor; and said differential pressure
transducer and said tachometer being in communication with said
controller; and said controller being programmed to determine the
instantaneous flow rate and current accumulated volume of
inspiratory gas flow delivered by said ventilator based on the
pressure differential measured by said differential pressure
transducer and the rotational speed measured by said
tachometer.
21. The ventilator of claim 1 wherein said compressor incorporates
a controller-readable data base containing specific rotational
speed, differential pressure and flow rate data for that particular
compressor; and wherein said controller is further programmed to
read said data base and to utilize information obtained from said
data base in the calculation of inspiratory flow, volume or
pressure delivered by said ventilator.
22. The ventilator of claim 21 wherein said controller-readable
data base comprises an EPROM.
23. The ventilator of claim 1 further in combination with a
portable battery for supplying power to said device.
24. The ventilator of claim 23 wherein said portable battery
contains sufficient power to operate said mechanical ventilator
device for at least two hours.
25. A drag compressor apparatus for creating inspiratory gas flow
in a mechanical ventilator, said compressor apparatus comprising: a
housing having a gas inflow passageway and a gas outflow
passageway; a rotor rotatably mounted within said housing, said
rotor being configured and constructed such that rotation of said
rotor in a first direction will cause said rotor to a) draw gas in
said inflow passageway, b) compress said gas and c) expel said gas
out of said outflow passageway; a controller for controlling the
rotation of said rotor within said housing, said controller being
operative to cause said rotor to intermittently accelerate and
decelerate so as to deliver discrete periods of inspiratory gas
flow through said outflow passageway.
26. The compressor of claim 25 wherein said rotor incorporates at
least one series of blades having leading edges, each of said
blades being disposed at a positive angle of attack such that, when
said rotor is rotated in said first direction, the leading edge of
each blade will precede the remainder thereof.
27. The compressor of claim 26 wherein said blades are disposed at
angles of attack of 30-60 degrees.
28. The compressor of claim 27 wherein said blades are disposed at
55 degree angles of attack.
29. The compressor of claim 26 wherein said blades are disposed at
spaced intervals within an annular trough which extends about said
rotor such that, when said rotor is rotating said first direction,
said blades will serially contact and compress gas within said
housing.
30. The compressor of claim 29 wherein said housing is further
configured to define therewithin at least one compressor flow path
said flow path being positioned in relation to said annular trough
and being connected to said inflow and outflow passageways such
that, when said rotor is rotated in said first direction, the
blades of said rotor will a) draw gas inwardly through said inflow
passageway into said compressor flow path, b) compress said gas
within said compressor flow path, and c) expel said gas out of said
outflow passageway.
31. The compressor of claim 31 wherein each of said blades has a
leading edge and at least one peripheral edge, and wherein said
blades are mounted within said trough such that the leading edges
of the blades extend transversely across the trough and the
peripheral edge of said blades are in abutment with said
trough.
32. The compressor of claim 30 wherein said at least one concave
annular trough comprises: a first annular trough which extends
about the periphery of said rotor on a first side thereof; and, a
second annular trough which extends about the periphery of said
rotor on a second side thereof.
33. The compressor of claim 32 wherein said housing is configured
to define therewithin: a first compressor flow path which is at
least partially within said first annular trough and is connected
to said inflow passageway and said outflow passageway; and, a
second compressor flow path which is at least partially within said
second annular trough and is connected to said inflow passageway
and said outflow passageway; said first and second compressor flow
paths being configured and positioned such that, when said rotor is
rotated in said first direction, the blades mounted within said
first annular trough will draw gas into said inflow passageway,
compress said gas within said first flow path, and expel said gas
out of said outflow passageway and the blades mounted within said
second annular trough will draw gas into said inflow passageway,
compress sid gas within said second flow path, and expel said gas
out of said outflow passageway.
34. The compressor of claim 33 wherein said first concave trough
and the blades mounted therewithin are mirror images of said second
concave trough and the blades mounted therewithin.
35. The compressor of claim 25 further comprising a drive motor
located within said compressor housing and coupled to said rotor to
rotatably drive said rotor.
36. The compressor of claim 25 wherein said housing further
comprises a number of heat dissipation fins formed on the outside
of the portion of said housing wherein said motor is positioned to
facilitate dissipation of heat from said motor.
37. The compressor of claim 35 further comprising a tachometer for
measuring the rotational speed of said rotor.
38. The compressor of claim 37 wherein said tachometer comprises an
optical encoder.
40. The compressor of claim 25 further comprising: a differential
pressure transducer for measuring the difference between the
pressure of gas in said inflow passageway and the pressure of gas
in said outflow passageway.
41. An exhalation valve for controlling the expiratory gas flow
from a mammalian patient, said exhalation valve comprising: a
housing defining an expiratory gas flow passageway therethrough; a
valve seat formed within said expiratory gas flow passageway; an
annular diaphragm movably disposed within said gas flow passageway,
in juxtaposition to said valve seat, said diaphragm being variably
movable back and forth to various positions between and including:
i) a fully closed position wherein said diaphragm is firmly seated
against said valve seat to prevent gas from flowing through said
passageway; and ii) a fully open position wherein said diaphragm is
retracted away from said annular valve seat so as to permit
substantially unrestricted flow of expiratory gas through said
pathway; an elongate actuation shaft having a proximal end and a
distal end, the distal end of said actuation shaft being
contractable with said diaphragm, and said actuation shaft being
axially moveable back and forth to control the positioning of said
diaphragm between said fully closed and said fully open positions;
an electrical induction coil linked to said actuation shaft such
that a decrease in the current passing into said induction coil
will cause said shaft to advance in the distal direction and an
increase in the current passing into said induction coil will cause
said shaft to retract in the proximal direction; means for
determining the flow rate of expiratory gas passing out of said
exhalation valve; means for determining airway pressure; a
microprocessor controller connected to said means for determining
airway pressure, said controller being provided with a positive
expiratory pressure setting, and said controller being connected to
said induction coil and adapted to emit control signals to said
induction coil to control the movement of said actuation shaft in
response to the current airway pressure, thereby maintaining the
present amount of positive expiratory pressure; a radio frequency
transponder database containing flow characterization data for the
means for determining the flow rate of expiratory gas passing out
of said exhalation valve; said controller being further connected
to said means for determining the flow rate of expiratory gas
passing out of said exhalation valve and being equipped to receive
radio frequency input of the characterization data contained in the
radio frequency transponder database, and to utilize such data to
determine the instant flow rate of expiratory gas passing out of
said exhalation valve.
43. The exhalation valve of claim 42 wherein said controller is
located separately from, said exhalation valve.
44. The exhalation valve of claim 41 wherein said controller is
further adapted to receive input signals from said means for
determining the flow rate at which expiratory gas is passing
outwardly through said expiratory gas flow passageway, and for
emitting control signals to said induction coil to fully close said
diaphragm when said flow rate has fallen to a predetermined basal
level, thus signifying the end of the expiratory phase.
45. A method of providing pulmonary ventilation to a mammalian
patient, said method comprising the steps of: a) providing a rotary
drag compressor device comprising: i) a housing having an inflow
passageway and an outflow passageway formed therein; and, ii) a
rotor rotatably mounted within said housing such that rotation of
said rotor in a first direction will draw gas into said inflow
passageway, compress said gas, and expel said gas out of said
outflow passageway; b) connecting the outflow passageway of said
rotary drag compressor to a conduit through which respiratory gas
flow may be passed into the patient's lungs; c) accelerating said
rotor to a first rotational speed for sufficient time to deliver a
desired inspiratory gas flow through said conduit and into the
patient's lungs; d) stopping said rotor or decelerating said rotor
to a basal rotational speed to terminate the inspiratory gas flow
through said conduit and to allow the expiratory phase of the
ventilation cycle to occur.
46. The method of claim 45 wherein step b comprises connecting said
overflow passageway to an endotracheal tube inserted into the
trachea of the patient.
47. The method of claim 45 wherein step b comprises connecting said
outflow passageway to a nasotracheal tube inserted into the trachea
of the patient.
48. The method of claim 45 wherein step b comprises connecting said
outflow passageway to a tracheostomy tube inserted into the trachea
of the patient.
49. The method of claim 45 wherein step b comprises connecting said
outflow passageway to a mask which is positioned over the nose and
mouth of the patient.
50. The method of claim 45 wherein step c is commenced upon the
occurrence of a triggering event, said triggering event being
selected from the group of triggering events consisting of: i) the
passing of a predetermined time period; and ii) the initiation of
spontaneous inspiratory effort by the patient.
51. The method of claim 45 wherein the inspiratory gas flow
delivered in step c is limited by a limiting parameter selected
from the group of limiting parameters consisting of: i. a
predetermined minimum airway pressure; ii. a predetermined maximum
airway pressure; iii. a predetermined minimum flow rate; iv. a
predetermined maximum flow rate; v. a predetermined minimum tidal
volume; and vi. a predetermined maximum tidal volume.
52. The method of claim 45 wherein step c is terminated and step d
is commenced upon the occurrence of a selected terminating event,
said terminating event being selected from the group of terminating
events consisting of: i. the passing of a predetermined period of
time since the commencement of step c; ii. the attainment of a
predetermined airway pressure; and iii. the passage of a
predetermined tidal volume of inspiratory gas.
53. The method of claim 45 wherein step c further comprises
controlling the speed to which said rotor is accelerated during the
inspiratory phase by: i. storing specific rotor speed, compressor
differential pressure and flow rate characterization data for the
compressor; ii. providing a first input signal to said compressor
which is intended to cause the rotor to rotate at a speed
calculated to deliver a desired flow rate; iii. determining the
actual flow rate generated by said compressor in response to said
first input signal; iv. comparing the actual flow rate determined
in step iii, to the desired flow rate; v. adjusting the input
signal to said compressor to provide the desired flow rate.
54. The method of claim 53 wherein step c further comprises: vi.
repeating steps ii-v, as necessary to achieve said desired flow
rate.
55. A rotary drag compressor ventilator device for delivering
inspiratory gas flow to a mammalian patient, said device
comprising: a) a rotary drag compressor having an intake port and
an outflow port; b) an inspiratory gas flow passageway for carrying
gas from the outflow port of the compressor to the patient during
the inspiratory phase of the ventilation cycle; c) means for
accelerating said compressor at the beginning of the inspiratory
phase of the ventilation cycle to deliver inspiratory gas flow
through said passageway to said patient; d) means for controlling
said compressor during the inspiratory phase of the ventilation
cycle to maintain a desired inspiratory pressure and flow rate;
and, e) means for decelerating said compressor at the end of the
inspiratory phase of the ventilation cycle.
56. The ventilator device of claim 55 wherein said inspiratory gas
flow passageway is devoid of valves for diverting the inspiratory
gas flow away from said patient.
57. The ventilator device of claim 55 wherein said rotary drag
compressor comprises: a compressor housing having said intake and
outflow ports formed therein; a rotor mounted within said housing
such that rotation of said rotor in a first direction will cause
said inspiratory gas flow to be delivered out of said outflow port
and through said inspiratory gas flow passageway to said patient;
and, a motor for rotating said rotor within said housing.
58. The ventilator device of claim 55 wherein said means for
accelerating, controlling and decelerating said compressor
comprise: a microprocessor controller connected to said
compressor.
59. The ventilator device of claim 55 further comprising: f) an
exhalation conduit for carrying expiratory gas flow from said
patient during the expiratory phase of the ventilation cycle; g) an
exhalation valve positioned on said exhalation conduit, said
exhalation valve being constructed to: i) open during the
expiratory phase of the ventilation cycle to permit the expiratory
gas flow to pass out of said exhalation conduit, and ii) close
during the inspiratory phase of the ventilation cycle to prevent
gas from being drawn into said patient through said exhalation
conduit.
60. The ventilator device of claim 55 further comprising: f) an
oxygen blending apparatus connected to said intake port to provide
oxygen-enriched air to said compressor.
61. An exhalation valve comprising: a) a housing defining a first
exhalation passageway through which expiratory gas may outflow in a
first direction; b) a valve seat formed within said passageway; c)
a diaphragm having a front side and a back side, said diaphragm
being sized and configured such that the front side thereof may
abut against said valve seat valve seat to thereby block the flow
of gas through said exhalation passageway, said diaphragm being
moveable back and forth between; i) a first position wherein said
diaphragm is fully retracted from said valve seat to permit
unrestricted flow through said passageway; ii) a second position
wherein said diaphragm is seated on said valve seat to block flow
through said passageway; iii) a range of intermediate positions
between said first and second positions wherein said diaphragm will
cause varying degrees of restriction of the flow through said
passageway; d) an elongate shaft having a first end and a second
end, the first end of said shaft being adjacent to the back side of
said diaphragm, said shaft being axially moveable back and forth
between; i) a first position wherein the first end of said shaft is
at a location which will retain said diaphragm in its first
position; ii) a second position wherein the first and of said shaft
is at a location which will allow said diaphragm to move to its
second position; and, iii) a range of intermediate positions
wherein said shaft is at a location which will allow said diaphragm
to move to one of its intermediate positions; e) an electrical
induction coil slidably mounted within said housing so as to move
back and forth in response to changes in current applied to the
coil, said coil consisting essentially of multiple convolutions of
wire upon which a rigidifying coating has been applied to hold said
wire in a closely coiled substantially cylindrical configuration;
f) a mounting spider connecting said shaft to said coil, said
spider configured to hold said shaft in co-axial alignment with the
longitudinal axis of the coil, with the first end of the shaft
protruding toward the back side of said diaphragm such that, when
the coil moves forward, said shaft will move forward toward said
first shaft position, and when said coil moves rearward, said shaft
will be retracted toward said second shaft position.
62. The exhalation valve of claim 61 wherein the front surface of
said diaphragm is planar and wherein said valve seat is angled
relative to the plane of the front surface of the diaphragm such
that, when said diaphragm is moving into said first diaphragm
position, the front side of said diaphragm will initially contact
only one side of said diaphragm and will subsequently move into
contact with the remainder of said valve seat.
63. The exhalation valve of claim 61 further comprising: g) a
pliable dust barrier disposed between said valve seat and said
induction coil, said pliable dust barrier being sealed to the
surrounding housing to prevent particulate matter from passing
around said shaft and into said induction coil, said dust barrier
being in contact with said shaft and being sufficiently flexible to
move back and forth in accordance with axial movement of said
shaft.
64. The exhalation valve of claim 63 wherein said dust barrier
comprises an elastomeric boot.
65. The exhalation valve of claim 63 wherein at least one vent hole
is formed in said exhalation valve to prevent the creation of
pressure on at least one side of said dust barrier as said dust
barrier flexes back and forth.
66. An exhalation valve comprising: a) a housing defining an
expiratory gas flow path connectable to a mammalian patient such
that expiratory gas exhaled by the patient will pass through said
flow path in a first direction; b) a valve associated with said
flow path to permit gas exhaled by the patient to pass through said
flow path in said first direction, but to prevent gas from being
drawn through said flow path, in a second direction opposite said
first direction, when said patient inhales; c) a flow measuring
apparatus for monitoring the flow rate of expiratory gas passing
through said exhalation valve.
67. The exhalation valve of claim 66 wherein said flow measuring
apparatus comprises: a flapper disposed transversely within said
flow path, said flapper being constructed such that at least a
portion of said flapper will deflect in a first direction when
exhaled gas is passed through said flow path in said first
direction, the extent of flapper deflection being variable with the
flow rate of gas passing through the exhalation valve, said flapper
thereby creating a dynamic flow restricting orifice within said
flow path; means for determining gas pressure within said flow path
upstream of said flapper; means for determining gas pressure within
said flow path downstream of said flapper; and means for
determining the then-current flow rate of gas passing through said
exhalation valve, based on the difference in the pressures measured
upstream and downstream of said flapper.
68. The exhalation valve device of claim 72 wherein said flapper is
mounted within a flapper assembly which comprises: a sheet of
pliable material having a first side, a second side and an outer
peripheral edge, a semi-annular cut being formed in said sheet to
divide said sheet into i) an outer peripheral portion which is
outboard of said cut and ii) an inner flapper portion which is
inboard of said cut, and which remains attached on one side thereof
to the surrounding peripheral portion of said sheet, said inner
flapper portion of said sheet being thereby deflectable back and
forth while the outer peripheral portion of said sheet is held in
substantially stationary position; a first frame member having a
central aperture formed therein, said first frame member being
juxtaposed to the first side of said sheet such that said first
frame member is in contact with the first side of the peripheral
portion of said sheet such that said first frame member is in
abutment with the first side of the peripheral portion of said
sheet and the central aperture of said first frame member surrounds
the first side of the flapper portion of said sheet; a second frame
member having a central aperture formed therein, said second frame
member being juxtaposed to the second side of said sheet such that
said frame member abuts against the second side of the peripheral
portion of said sheet, and the central aperture of said second
frame member surrounds the second side of the flapper portion of
said sheet; said first and second frame members thereby holding the
peripheral portion of said sheet in a substantially fixed position
between said frame members while the flapper portion of said sheet
extends transversely into the space between the axially aligned
apertures of said frame members and is deflectable back and forth
therein.
69. The exhalation valve device of claim 68 wherein said flapper
assembly is positioned transversely within the flow path of said
exhalation valve and is held in such position by engagement to the
surrounding exhalation valve housing.
70. The exhalation valve device of claim 66 further comprising:
specific flow-pressure calibration information for the flow
measuring apparatus stored on a storage medium contained within the
exhalation valve housing.
71. The exhalation valve device of claim 70 wherein said storage
medium comprises a radio-frequency transponder.
72. The exhalation valve device of claim 70 wherein the
characterization information stored on said storage medium
comprises a data base of predetermined pressure differences for
specific flow rates of exhalation valve.
73. The exhalation valve device of claim 70 wherein the information
stored on said storage medium comprises an equation for calculating
specific flow rates based on measured pressure differentials for
that exhalation valve.
74. The exhalation valve device of claim 68 further comprising: a
cushioning washer and a third frame member disposed on at least one
of the first and second frame members which abut against the same
so as to evenly distribute stresses applied to said sheet by said
frame members.
75. The exhalation valve device of claim 74 wherein said cushioning
washer comprises an elastomeric material disposed on said third
frame member.
76. An oxygen blending apparatus for delivering oxygen enriched air
to a ventilator, said apparatus comprising: a) an accumulator
chamber; b) an air inlet conduit connected to said accumulator
chamber; c) an oxygen inlet conduit connected to said accumulator
chamber; d) a series of solenoid valves connected, in parallel,
within said oxygen inlet conduit, each of said solenoid valves
having a predetermined orifice size; and e) a controller for
independently opening and closing each of the solenoid valves to
control the amount of oxygen which flows into the accumulator
chamber during a time period.
77. The oxygen blending apparatus of claim 76 further in
combination with a ventilator device connected to the outlet of
said accumulator chamber, said ventilator device being operative to
intermittently draw inspiratory gas from said accumulator chamber
to compress and expel said gas to provide an inspiratory flow.
78. The oxygen blending apparatus of claim 77 wherein said
controller is further programmed to repeatedly determine the volume
of oxygen enriched gas which has been drawn from the accumulator
chamber during the then-current inspiratory phase, and to
subsequently adjust the opening and closing of the solenoid valves
to maintain the prescribed oxygen concentration of gas drawn from
the accumulator chamber during the reminder of that inspiratory
phase.
79. The oxygen blending apparatus of claim 78 wherein said
controller is further programmed to repeatedly compare the
then-current accumulated volume of oxygen enriched gas to a
predetermined trigger volume for each of the solenoid valves, and
to open each solenoid valve for a predetermined period of time when
it is determined that the accumulated volume of oxygen-enriched air
has exceeded the trigger volume for that individual solenoid
valve.
80. The oxygen blending apparatus of claim 76 wherein said solenoid
valves comprise at least first, second, third and fourth solenoid
valves, and wherein a predetermined oxygen pressure is constantly
passed into said oxygen inlet conduit.
81. The oxygen blending apparatus of claim 80 wherein said first,
second, third, and fourth solenoid valves have flow rates, at a
predetermined oxygen inlet operating pressure, of 5 liters/min.,
14.7 liters/min.; 40 liters/min. and 80 liters/min.,
respectively.
82. The oxygen blending apparatus of claim 76 wherein the
ventilator device connected to the outlet of the accumulator
chamber comprises the ventilator device of claim 55.
83. The oxygen blending apparatus of claim 82 wherein the
controller which controls opening and closing of the solenoid
valves is incorporated into the means for controlling the
ventilator compressor.
84. A flow transducer for measuring the flow rate of a fluid, said
transducer comprising: a housing defining a first fluid flow path
therethrough; a deflectable flapper disposed transversely within
said fluid flow path such that said flapper will deflect in the
direction of fluid flow, thereby creating a fluid flow restriction
permitting some fluid to flow past said flapper and through said
flow path; a first pressure port located upstream of said flapper
for measuring the pressure of fluid within said flow path, upstream
of said flapper; a second pressure port downstream of said flapper
for measuring the pressure of fluid flowing through said flow path,
downstream of said flapper; means associated with first pressure
port for determining the pressure of fluid flowing upstream of said
flapper; means associated with said second pressure port for
determining the pressure of fluid flowing downstream of said
flapper; means for determining the difference between the pressure
of fluid flowing upstream of said flapper and the pressure of fluid
flowing downstream of said flapper; and means for computing the
flow rate of fluid through said flow path, based on the measured
difference in pressures upstream and downstream of said
flapper.
85. The fluid flow transducer of claim 84, wherein said deflectable
flapper comprises: a rigid frame having a central aperture formed
therein; a flat sheet of pliable material mounted within said frame
member and forming a flapper disposed transversely within the
central aperture of said frame and deflectable in at least one
direction to permit fluid to flow past said flapper and through
said central aperture; said frame being mounted transversely within
said flow path such that fluid flowing in a first direction through
said flow path will strike said flapper, thereby causing said
flapper to deflect in the direction of flow such that the flowing
fluid may pass through said central aperture.
86. The flow transducer of claim 85 wherein: said flat sheet of
pliable material comprises an outer peripheral portion, an inner
flapper portion, and a semi-annular cut formed in said sheet to
free most of said peripheral portion from said flapper portion; and
said rigid frame comprises first and second frame members disposed
on opposite sides of the peripheral portion of said flat sheet,
said frame members being compressed inwardly to compressively hold
said peripheral portion of said flat sheet between said frame
members such that the flapper portion of said flat sheet is
transversely disposed and deflectable within the central aperture
of said frame.
87. The flow transducer of claim 84 further comprising: a
cushioning member associated with said flapper to distribute the
force exerted on said flapper thereby distributing any stresses
created within said flapper.
88. The flow transducer of claim 85 further comprising: a
cushioning member associated with said frame to distribute the
force exerted by said frame on said flat sheet of pliable material,
thereby distributing any stresses of created within said flat sheet
of pliable material.
89. The flow transducer of claim 84 wherein said housing comprises
a portion of an exhalation valve through which a mammalian patient
is permitted to exhale, said flow transducer being disposed within
said exhaltion valve to measure the flow rate of expiratory gas
passing through said exhalation valve.
90. The flow transducer of claim 84 further comprising: a deflector
member positioned on at least one of said first and second pressure
ports to deter fluid from being forced directly into the pressure
port on which deflector insert is positioned.
91. The flow transducer of claim 84 wherein said means for
computing flow rate comprises a microprocessor.
92. The flow transducer of claim 86 wherein: said housing
incorporates first and second abutment ridges formed about-said
flow path; said first and second frame members, having said flat
sheet of pliable material therebetween, being positioned between
said abutment ridges such that said abutment ridges will exert
inward compressive force on said first and second frame members to
compressively hold said flat sheet therebetween.
93. The flow transducer of claim 84 further comprising: specific
flow-pressure calibration information for the flow transducer
stored on a storage medium contained within said housing.
94. The flow transducer of claim 93 wherein said storage medium
comprises a radio-frequency transponder.
95. The flow transducer of claim 93 wherein the specific
flow-pressure calibration information stored on said storage medium
comprises a data base of predetermined pressure differences for
specific flow rates of fluid through said flow path.
96. The flow transducer of claim 93 wherein the calibration
information stored on said storage medium comprises an equation for
calculating specific flow rates based on measured differences in
pressure upstream and downstream of said flapper.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains generally to medical
equipment and more particularly to a compressor powered mechanical
ventilator device for delivering respiratory ventilation to a
mammalian patient.
BACKGROUND OF THE INVENTION
A. Principles of Mechanical Ventilation
[0002] In many clinical settings mechanical ventilators are used to
facilitate the respiratory flow of gas into and out of the lungs of
patients who are sick, injured or anesthetized.
[0003] In general, mechanical ventilators provide a repetitive
cycling of ventilatory flow, each such repetitive cycle being
separated into two phases--an inspiratory phase followed by an
expiratory phase.
[0004] The inspiratory phase of the ventilator cycle is
characterized by the movement of positive-pressure inspiratory flow
of gas through the ventilator circuit and into the lungs of the
patient. The expiratory phase of the ventilatory cycle is
characterized by cessation of the positive pressure inspiratory
flow long enough to allow lung deflation to occur. The exhaled gas
is vented from the ventilator circuit, typically through an
exhalation valve. In patient whose lungs and thoracic musculature
exhibit normal compliance, the act of exhalation is usually
permitted to occur spontaneously without mechanical assistance from
the ventilator.
[0005] It is sometimes desirable to control the airway pressure
during exhalation to maintain a predetermined amount of positive
back pressure during all, or a portion of, the respiratory cycle.
Such techniques are often utilized to treat impairments of lung
capacity due to pulmonary atelectasis or other factors.
[0006] The mechanical ventilators of the prior art have been
grouped under various classification schemes, based on various
criteria. In general, mechanical ventilators may be grouped or
classified according to the parameter(s) which are utilized for a)
triggering, b) limiting and c) terminating (e.g., cycling) the
inspiratory phase of the ventilator cycle.
[0007] "Triggering" is the action that initiates the inspiratory
phase of the ventilator cycle. The initiation of the inspiratory
phase may be triggered by the ventilator or the patient. The
variables and/or parameters which are utilized to trigger the
beginning of the inspiratory phase include: time (i.e., respiratory
rate), the commencement of spontaneous inhalation by the patient
and/or combinations thereof.
[0008] "Limiting" of the inspiratory phase refers to the manner in
which the inspiratory gas flow is maintained within prescribed
ranges to optimize the ventilation of the patient's lungs. The
limiting variables and/or parameters are typically controlled by
the ventilator, but may change as a result of patient effort and/or
physiologic variables such as lung compliance and airway
resistance. The variables and/or parameters which are utilized for
limiting the inspiratory phase include flow rate, airway pressure
and delivered volume.
[0009] "Terminating" or "cycling" of the inspiratory phase of the
ventilator cycle refers to the point at which the inspiratory flow
is stopped and the ventilator and/or patient are permitted to
"cycle" into the expiratory phase. Depending on the ventilator
control settings, the termination of the inspiratory phase may be
brought about by the ventilator or the patient. The variables
and/or parameters which are utilized to terminate the inspiratory
phase include: time; peak airway pressure; and/or tidal volume
(V.sub.t).
B. Mechanical Ventilation Modes Utilized in Modern Clinical
Practice
[0010] In addition Mechanical ventilators are utilized to deliver
various "modes" of mechanical ventilation, the particular mode of
ventilation being selected or prescribed based on the clinical
condition of the patient and the overall objective (i.e., long term
ventilation, short term ventilation, weaning from ventilator, etc .
. . ) of the mechanical ventilation.
I. Ventilation Modes
[0011] i. Intermittent Mandatory Ventilation (IMV)
[0012] Intermittent Mandatory Ventilation is a ventilation mode
wherein a spontaneously breathing patient receives intermittent
mechanical inflation supplied asynchronously by the ventilator.
[0013] ii. Synchronized Intermittent Mandatory Ventilation
(SMIV)
[0014] Synchronized Intermittent Mandatory Ventilation is a
ventilation mode wherein a spontaneously breathing patient receives
occasional mandatory ventilatory breaths. Mandatory ventilator
breaths are synchronized with the patient's spontaneous inspiratory
efforts.
[0015] iii. Controlled Mechanical Ventilation (CMV)
[0016] Controlled Mechanical Ventilation (CMV) is a ventilation
mode wherein mechanical breaths are delivered to the patient at
time intervals which are unaffected by patient efforts. Controlled
Mechanical Ventilation is typically utilized in patients who are
not breathing spontaneously.
[0017] iv. Assist/Control Ventilation (A/C)
[0018] Assist/Control Ventilation (A/C) is a ventilation mode
wherein the patient is able to volitionally alter the frequency of
mandatory ventilator breaths received, but can not alter the flow
and title volume (V.sub.t) of each ventilator breath received.
Controlled, mandatory breaths are initiated by the ventilator based
on the set breath rate. In addition, the patient can demand and
trigger an assist breath. After successful triggering of an assist
breath, the exhalation valve is closed and gas is delivered to the
patient to satisfy the preset tidal volume, peak flow and wave
form.
C. Breath Types Utilized in Modern Clinical Practice
[0019] Breath types are typically classified according to the
particular functions which control:
[0020] a) triggering;
[0021] by) limiting; and
[0022] c) cycling of each breath delivered by the mechanical
ventilator, as described and defined hereabove.
[0023] Typical breath types and ventilator parameters utilized in
modern clinical practice include the following:
[0024] i. Machine-Cycled--Mandatory Breath
[0025] A machine-cycled, mandatory breath is a breath that is
triggered, limited and cycled by the ventilator.
[0026] ii. Machine-Cycled--Assist Breath
[0027] A machine cycled assist breath is a breath that is triggered
by the patient, but is limited and cycled by the ventilator.
[0028] iii. Patient-Cycled--Supported Breath
[0029] A patient-cycled, supported breath is a breath that is
triggered by the patient, limited by the ventilator, and cycled by
the patient.
[0030] iv. Patient-Cycled--Spontaneous Breath
[0031] A patient-cycled spontaneous breath is a breath that is
triggered, limited and cycled by the patient. While patient effort
limits the flow, and hence the inspiratory volume of the breath,
the ventilator may also limit the breath by providing a flow that
is to low to maintain a constant pressure in the face of patient
inspiratory demand.
[0032] v. Volume-Controlled Mandatory Breaths
[0033] Volume-controlled breaths are machine-triggered mandatory
breaths. The inspiratory phase is initiated by the ventilatory
based on a preset breath rate. The inspiratory phase is ended, and
the expiratory phase begun, when the breath delivery is determined
to be complete based on a preset tidal volume, peak flow and wave
form setting. The ventilator remains in expiratory phase until the
next inspiratory phase begins.
[0034] vi. Volume-Controlled--Assist Breaths
[0035] Volume-controlled breaths are machine cycled supported
breaths that are initiated by the patient. Volume-controlled assist
breaths may be initiated only when the "assist window" is open. The
"assist window" is the interval or time during which the ventilator
is programmed to monitor inspiratory flow for the purpose of
detecting patient inspiratory effort. When a ventilator breath is
triggered, the inspiratory phase of such breath will continue until
a preset tidal volume peak flow and wave form have been achieved.
Thereafter, the exhalation valve is open to permit the expiratory
phase to occur. The ventilatory remains in the expiratory phase
until the next patient-triggered breath, or the next mandatory
inspiratory phase, begins.
[0036] vii. Pressure-Controlled Breaths
[0037] Pressure-Controlled breaths are delivered by the ventilator
using pressure as the key variable for limiting of the inspiratory
phase. During pressure control, both the target pressure and the
inspiratory time are set, and the tidal volume delivered by the
ventilator is a function of these pressure and time settings. The
actual tidal volume delivered in each pressure-controlled breath is
strongly influenced by patient physiology.
[0038] viii. Pressure Support Breaths
[0039] Pressure support breaths are triggered by the patient,
limited by the ventilator, and cycled by the patient. Thus, each
breath is triggered by patient inspiratory effort, but once such
triggering occurs the ventilator will assure that a predetermined
airway pressure is maintained through the inspiratory phase. The
inspiratory phase ends, and the expiratory phase commences, when
the patients inspiratory flow has diminished to a preset baseline
level.
[0040] ix. Sigh Breaths
[0041] A sigh breath is a machine-triggered and cycled,
volume-controlled, mandatory breath, typically equal to 1.5 times
the current tidal volume setting. The inspiratory phase of each
sigh breath delivers a preset tidal volume and peak flow. The
duration of the inspiratory phase of each sigh breath is limited to
a maximum time period; typically 5.5 seconds. The ventilator may be
set to deliver a sigh function automatically after a certain number
of breaths or a certain time interval (typically 100 breaths for
every 7 minutes), which ever interval is shorter. The sigh breath
function it may be utilized during control, assist and SIMV modes
of operation, and is typically disabled or not utilized in
conjunction with pressure controlled breath types or continuous
positive air way pressure (CPAP).
[0042] x. Proportional Assist Ventilation (PAV)
[0043] Proportional Assist Ventilation (PAV) is a type of
ventilator breath wherein the ventilator simply amplifies the
spontaneous inspiratory effort of the patient, while allowing the
patient to remain in complete control of the tidal volume, time
duration and flow pattern of each breath received.
[0044] xi. Volume Assured Pressure Support (VAPS)
[0045] Volume Assured Pressure Support (VAPS) is a type of
ventilator breath wherein breath initiation and delivery is similar
to a pressure support breath. Additionally, the ventilator is
programmed to ensure that a preselected tidal volume (V.sub.t) is
delivered during such spontaneously initiated breath.
D. Oxygen Enrichment of the Inspiratory Flow
[0046] It is sometimes desirable for mechanical ventilators to be
equipped with an oxygen-air mixing apparatus for oxygen enrichment
of the inspiratory flow. Normal room air has an oxygen content
(FiO.sub.2) of 21%. In clinical practice, it is often times
desirable to ventilate patients with oxygen FiO.sub.2 from 21% to
100%. Thus, it is desirable for mechanical ventilators to
incorporate systems for blending specific amounts of oxygen with
ambient air to provide a prescribed oxygen-enriched FiO.sub.2.
Typically, volume-cycle ventilators which utilize a volume
displacement apparatus have incorporated oxygen mixing mechanisms
whereby compressed oxygen is combined with ambient air to produce
the selected FiO.sub.2 as both gases are drawn into the
displacement chamber during the expiratory phase of the ventilator
cycle. Nonbellows-type volume-cycled ventilators have incorporated
other air-oxygen blending systems for mixing the desired relative
volumes of oxygen and air, and for delivering such oxygen-air
mixture through the inspirations circuitry of the ventilator.
E. Regulation/Control of Expiratory Pressure
[0047] The prior art has included separately controllable
exhalation valves which may be preset to exert desired patterns or
amounts of expiratory back pressure, when such back pressure is
desired to prevent atelectasis or to otherwise improve, the
ventilation of the patient.
[0048] The following are examples of expiratory pressure modes
which are frequently utilized in clinical practice:
[0049] i. Continuous Positive Airway Pressure (CPAP)
[0050] Continuous Positive Airway Pressure (CPAP) is employed
during periods of spontaneous breathing by the patient. This mode
of ventilation is characterized by the maintenance of a
continuously positive airway pressure during both the inspiratory
phase, and the expiratory phase, of the patient's spontaneous
respiration cycle.
[0051] ii. Positive End Expiratory Pressure (PEEP)
[0052] In Positive End Expiratory Pressure a predetermined level of
positive pressure is maintained in the airway at the end of the
expiratory phase of the cycle. Typically, this is accomplished by
controlling the exhalation valve so that the exhalation valve may
open only until the circuit pressure has decreased to a preselected
positive level, at which point the expiration valve closes again to
maintain the preselected positive end expiratory pressure
(PEEP).
F. Portable Ventilators of the Prior Art
[0053] The prior art has included some non-complex portable
ventilators which have inherent limitations as to the number and
type of variables and/or parameters which may be utilized to
trigger, limit and/or terminate the ventilator cycle. Although such
non-complex ventilators of the prior art are often sufficiently
power efficient and small enough for portable use, their functional
limitations typically render them unsuitable for long term
ventilation or delivery of complex ventilation modes and or breath
types.
[0054] The prior art has also included non-portable, complex
microprocessor controlled ventilators of the type commonly used in
hospital intensive care units. Such ventilators typically
incorporate a microcomputer controller which is capable of being
programmed to utilize various different variables and/or parameters
for triggering, limiting and terminating the inspiratory phase of
the ventilator cycle. Complex ventilators of this type are
typically capable of delivering many different ventilation modes
and or breath types and are selectively operable in various
volume-cycled, pressure cycled or time-cycled modes. However, these
complex ventilators of the prior art have typically been too large
in size, and too power inefficient, for battery-driven portable
use. As a result of these factors, most of the complex
micro-processor controlled ventilators of the prior art are
feasible for use only in hospital critical care units.
[0055] As is well known there exist numerous settings, outside of
hospital critical care units, where patients could benefit from the
availability of a small, battery powered, complex microprocessor
controlled mechanical ventilator capable of delivering extended
modes of ventilation. For example, critically ill patients
sometimes require transport outside of the hospital in various
transport vehicles, such as ambulances and helicopters. Also,
critical care patients are sometimes transiently moved, within the
hospital, from the critical care unit to various special procedure
areas (e.g., radiology department, emergency room, catheterization
lab etc.,) where they may undergo diagnostic or therapeutic
procedures not available in the critical care unit. Additionally,
patients who require long term ventilation are not always
candidates for admission to acute care hospital critical care units
or may be discharged to step-down units or extended care
facilities. Also, some non-hospitalized patients may require
continuous or intermittent ventilatory support. Many of these
patients could benefit from the use of complex microprocessor
controlled ventilators, but may be unable to obtain such benefit
due to the non-feasibility of employing such ventilators outside of
the hospital-critical care unit environment.
[0056] In view of the foregoing limitations on the usability of
prior art complex microprocessor controlled volume-cycled
ventilators, there exists a substantial need in the art for the
development of a portable, highly efficient, ventilator capable of
programmed delivery of various modern ventilatory modes and breath
types, while also being capable of use outside of the hospital
critical care unit environment, such as in transport vehicles,
extended care facilities and patients homes, etc.
[0057] U.S. Pat. No. 4,493,614 (Chu et al.) entitled "PUMP FOR A
PORTABLE VENTILATOR" describes a reciprocating piston pump which is
purportedly usable in a portable ventilator operable on only
internal or external battery power.
[0058] U.S. Pat. No. 4,957,107 (Sipin) entitled "GAS DELIVERY
MEANS" describes a rotating drag compressor gas delivery system
which is ostensibly small enough to be utilized in a portable
ventilator. The system described in U.S. Pat. No. 4,957,107
utilizes a high speed rotary compressor which delivers a
substantially constant flow of compressed gas. The rotary
compressor does not accelerate and decelerate at the beginning and
end of each inspiratory phase of the ventilator cycle. Rather, the
rotating compressor runs continuously, and a diverter value is
utilized to alternately direct the outflow of the compressor a)
into the patients lungs during the inspiratory phase of the
ventilation cycle, and b) through an exhaust pathway during the
expiratory phase of the ventilation cycle.
[0059] Thus, there remains a substantial need for the development
of an improved portable mechanical ventilator which incorporates
the following features:
[0060] A. Capable of operating for extended periods (i.e., at least
21/2 hours) using a single portable battery or battery pack as the
sole power source;
[0061] B. Programmable for use in various different ventilatory
modes, such as the above-described IMV, SMV, CMV, PAV, A/C and
VPAS.
[0062] C. Usable to ventilate non-intubated mask patients as well
as intubated patients.
[0063] D. Oxygen blending capability for delivering oxygen-enriched
inspiratory flow.
[0064] E. Capable of providing controlled exhalation back pressure
for CPAP or PEEP.
[0065] F. Portable, e.g., less than 30 lbs.
SUMMARY OF THE INVENTION
[0066] The present invention specifically addresses the above
referenced deficiencies and needs of the prior art by providing
comprises a mechanical ventilator device which incorporates a
rotary compressor for delivering intermittent inspiratory gas flow
by repeatedly accelerating and decelerating the compression rotor
at the beginning and end of each inspiratory-phase. Prior to
commencement of each inspiratory ventilation phase, the rotary
compressor is stopped, or rotated at a basal rotational speed. Upon
commencement of an inspiratory phase, the rotary compressor is
accelerated to a greater velocity for delivering the desired
inspiratory gas flow. At the end of each inspiratory phase, the
rotational velocity of the compressor is decelerated to the basal
velocity, or is stopped until commencement of the next inspiratory
ventilation phase. A programmable controller is preferably
incorporated to control the timing and rotational velocity of the
compressor. Additionally, the controller may be programmed to cause
the compressor to operate in various modes of ventilation, and
various breath types, as employed in modern clinical practice.
[0067] Further in accordance with the present invention, there is
provided an oxygen blending apparatus which may be utilized
optionally with the rotatable compressor ventilation device of the
present invention. The oxygen blending apparatus of the present
invention comprises a series of valves having flow restricting
orifices of varying size. The valves are individually opened and
closed to provide a desired oxygen enrichment of the inspiratory
gas flow. The oxygen blending apparatus of the present invention
may be controlled by a programmable controller associated with, or
separate from, the ventilator controller.
[0068] Still further in accordance with the invention, there is
provided an exhalation valve apparatus comprising a housing which
defines an expiratory flow path therethrough and a valving system
for controlling the airway pressure during the expiratory phase of
the ventilation cycle. A pressure transducer monitors airway
pressure during exhalation the output of which is used by the
controller to adjust the valving system to maintain desired airway
pressure.
[0069] In addition the present invention utilizes an exhalation
flow transducer to accurately measure patient exhalation flow which
may be utilized for determination of exhaled volume and desired
triggering of inspiratory flow. In the preferred embodiment, the
exhalation flow transducer is integrally formed with the exhalation
valve, however, those skilled in the art will recognize that the
same can be a separate component insertable into the system. To
insure transducer performance accuracy, in the preferred
embodiment, the particular operational characteristics of each flow
transducer are stored within a memory device preferably a
radio-frequency transponder mounted within the exhalation valve to
transmit the specific calibration information for the exhalation
flow transducer to the controller. Further, the particular
construction and mounting of the flow transducer within the
exhalation valve is specifically designed to minimize fabrication
inaccuracies.
[0070] Further objects and advantages of the invention will become
apparent to those skilled in the art upon reading and understanding
of the following detailed description of preferred embodiments, and
upon consideration of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0071] FIG. 1 is a basic schematic diagram of a preferred
ventilator system of the present invention incorporating, a) a
rotary compressor ventilator device, b) an optional air-oxygen
blending apparatus; and c) a controllable exhalation valve, and d)
a programmable controller or central processing unit (CPU) which is
operative to control and coordinate the functioning of the
ventilator, oxygen blending apparatus and exhalation valve.
[0072] FIG. 2 is a detailed schematic diagram of a ventilator
system of the present invention.
[0073] FIG. 3 is a front view of the control panel of a preferred
ventilator system of the present invention.
[0074] FIG. 4 is a perspective view of a preferred drag compressor
apparatus which may be incorporated into the ventilator system of
the present invention.
[0075] FIG. 5 is a longitudinal sectional view through line 5-5 of
FIG. 4.
[0076] FIG. 6 is an enlarged view of a segment of FIG. 5.
[0077] FIG. 7 is an enlarged view of a segment of FIG. 6.
[0078] FIG. 8 is an elevational view of a preferred drag compressor
component of a mechanical ventilator device of the present
invention.
[0079] FIG. 9 is a perspective view of the drag compressor
component of FIG. 8.
[0080] FIG. 10 is an enlarged view of a segment of FIG. 9.
[0081] FIG. 11a is a longitudinal sectional view of a preferred
exhalation valve of the present invention.
[0082] FIG. 11b is a perspective view of the preferred spider
bobbin component of the exhalation valve shown in FIG. 11a.
[0083] FIG. 11c is an exploded perspective view of a portion of the
exhalation valve of FIG. 11a.
[0084] FIG. 11d is a perspective view of a portion of the
exhalation valve shown in FIG. 11c.
[0085] FIG. 11e is an exploded perspective view of the preferred
flow restricting flapper component of the exhalation valve shown in
FIGS. 11a-11d.
[0086] FIG. 12 is a graphic example of flow vs. speed vs. pressure
data generated for a preferred exhalation valve of the present
invention, accompanied by an exhalation valve characterization
algorithm computed therefrom.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0087] The following detailed description and the accompanying
drawings are provided for purposes of describing and illustrating a
presently preferred embodiment of the invention and are not
intended to describe all embodiments in which the invention may be
reduced to practice. Accordingly, the following detailed
description and the accompanying drawings are not to be construed
as limitations on the scope of the appended claims.
A. General Description of the Preferred Ventilator System
[0088] With reference to FIGS. 1-2, the mechanical ventilation
system 10 of the present invention generally comprises a) a
programmable microprocessor controller 12, b) a ventilator device
14, c) an optional oxygen blending apparatus 16 and d) an
exhalation valve apparatus 18. Which is preferably implemented as a
portable, battery powered system.
[0089] The ventilator device 14 incorporates a rotating drag
compressor 30 which is driven by an electric motor 102. In response
to control signals received from controller 12, a bladed rotor
within the compressor 30 will undergo rotation for specifically
controlled periods of time and/or, within specifically controlled
parameters, so as to provide inspiratory gas flow through line 22
to the patient PT.
[0090] The controller 12 comprises a programmable microprocessor
which is electrically interfaced a) to the ventilator device 14 by
way of control line 13, b) to the optional oxygen blending
apparatus 16 by way of control line 17, and c) to the exhalation
valve 18 by way of control line 19 and also by RF communication
between flow transducer transponder (21) and transmitter/receiver
(23). Preferably incorporated into the exhalation valve 18 as will
be described in more detail infra.
[0091] The controller 12 is preferably programmed to utilize
selected parameters (e.g., time, flow rate, tidal volume (V.sub.t),
airway pressure, spontaneous breath initiation, etc.) for
triggering, limiting and cycling the inspiratory flow in accordance
with the selected ventilatory mode or breath type.
[0092] At the end of each inspiratory flow cycle, the patient PT is
permitted to exhale through exhalation valve 18. The flow rate or
pressure of the expiratory flow through exhalation valve 18 is
controlled by varying the degree of flow restriction within the
exhalation valve 18, in response to control signals received
through line 19 from controller 12. This enables the exhalation
valve 18 to be utilized to create a selected expiratory back
pressure (e.g., CPAP, PEEP).
[0093] Optional oxygen blending apparatus 16 may be utilized to
enrich the oxygen content of the inspiratory gas flow provided by
the drag compressor ventilator device 14. The preferred oxygen
blending apparatus 16 comprises a plurality of (preferably five
(5)) solenoid valves 52, each having a specific sized flow
restricting orifice. The solenoid valves 52 are arranged in
parallel between an oxygen inflow manifold 26 and an oxygen outflow
manifold 28. The controller 12 is programmed to open and close the
individual solenoid valves 52 for specific periods of time so as to
provide a metered flow of oxygen through oxygen outflow manifold 28
and into accumulator 54. Ambient air is drawn through conduit 24
and filter 50, into accumulator 54, where the ambient air combines
with the metered inflow of oxygen to provide an oxygen-enriched
inspiratory flow containing a prescribed oxygen concentration
(FIO.sub.2).
[0094] The presently preferred embodiment of the system 10 will
operate when supplied with voltage input within the range of 85-264
VAC at 50/60 Hz.
[0095] An AC power cord is preferably connectable to the system 10
to provide AC power input.
[0096] Additionally, the system 10 preferably includes an internal
battery capable of providing at least 15 minutes, and preferably 30
minutes, of operation. During internal battery operation, some
non-essential displays may be dimmed or disabled by the controller
12. The internal battery is preferably capable of being recharged
by AC power input provided through the AC power cable, or by a
separate battery charger. The internal battery is preferably
capable of being fully charged, from a no charged state, within 24
hours. The internal battery charge light 306 shown on the panel of
the preferred controller 12a may additionally flash if desired
during charging of the internal battery.
[0097] Also, the system may include an external battery or battery
set capable of providing at least 2 hours of operation, and
preferably capable of providing 4 to 8 hours of operation. During
external battery use, some non-essential displays may be dimmed or
disabled by the controller 12. The battery or battery set is
preferably capable of being recharged by delivery of AC power
through the AC power cable, or by a separate battery charger. It is
preferable that the external battery or battery set be capable of
being fully charged, from a no charged state within 24 to 48 hours.
The external battery charge light 310 on the panel of the preferred
controller 12a may additionally flash if desired during charging of
the external battery or battery set.
B. The Preferred Controller Apparatus
[0098] It will be appreciated that the controller 12 of the
ventilator system 10 of the present invention will vary in
complexity, depending on the specific capabilities of the system
10, and whether or not the optional oxygen blending apparatus 16 is
incorporated.
[0099] FIG. 3 shows the control panel of a preferred controller
apparatus 12a which is usable in connection with a relatively
complex embodiment of the ventilatory system 10, incorporating the
optional oxygen blending apparatus 16.
[0100] Controls Settings and Displays
[0101] The specific control settings and displays which are
included in the preferred controller 12a, and the ways in which the
preferred controller 12a receives and utilizes operator input of
specific control settings, are described herebelow:
[0102] 1. Standby-Off Control
[0103] The ventilator system 10 incorporates a stand by/off switch
(not shown) which turns the main power on or off. A group of
indicator lights 300 are provided on the face panel of the
controller 12a, and are more fully described herebelow under the
heading "monitors". In general, the panel indicator lights include
an "on" indicator 302 which becomes illuminated when the ventilator
is turned on. An AC power low/fail indicator light 304 activates
when the AC power cord is present and the voltage is out of a
specified operating range. Upon sensing low or faulty AC power, the
controller 12a will automatically switch the ventilator 14 to
internal battery power. The ventilator will continue to operate on
internal battery power until such time as power in the internal
battery reaches a minimum level. When the power in the internal
battery reaches a minimum level, the controller 12a will cause the
internal battery light and/or audible alarm 308 to signal that the
internal battery is near depletion.
[0104] A separate external battery light and/or audible alarm 312
is also provided. The external battery light and/or audible alarm
will activate when the external battery is in use, and has a
battery voltage which is out of the acceptable operation range.
During this condition, the controller 12a will cause all
nonessential displays and indicators to shut down.
[0105] When AC power is connected to the ventilator 14, but the
ventilator is turned off, any internal or external batteries
connected to the ventilator will be charged by the incoming AC
current. Internal battery charge indicator light 306 and external
battery charge indicator light 306 and external battery charged
indicator light 310 are provided, and will blink or otherwise
indicate charging of the batteries when such condition exists.
[0106] 2. Mode Select
[0107] A mode select module 320 incorporates plural, preferably
five (5) mode select buttons 322, 324, 326, 328, 330. Mode select
button 322 sets the system 10 for Assist Control (a/c). Mode select
button 324 sets the system 10 for Synchronized Intermittent
Mandatory Ventilation (SIV). Mode select button 326 sets the system
for Continuous Positive Airway Pressure (CPAP).
[0108] Spare mode select buttons 328, 330 are provided to permit
the controller 12a to be programmed for additional specific
ventilation modes such as volume assured pressure support (VAPS) or
proportional assist ventilation. When the controller is programmed
for additional specific ventilation modes, select buttons 328, 330
may be correspondingly labeled and utilized to set the ventilator
14 to deliver such subsequently programmed ventilation modes.
[0109] 3. Tidal Volume
[0110] A digital tidal volume display 332, with corresponding tidal
volume setting button 332a are provided. When tidal volume setting
button 332a is depressed, value setting knob 300 may be utilized to
dial in a selected tidal volume. The tidal volume display 332 will
then provide a digital display of the currently selected tidal
volume value.
[0111] The typical range of setable tidal volumes is 25 ml-2000
ml.
[0112] 4. Breath Rate
[0113] A digital breath rate display 334, with corresponding breath
rate setting button 334a is provided. When breath rate setting
button 334a is depressed, value setting knob 300 may be utilized to
dial in the desired breath rate. Breath rate display 334 will
thereafter display the currently selected breath rate.
[0114] The typical rage of selectable breath rates is 0 to 80
breaths per minute.
[0115] 5. Peak Flow
[0116] A digital peak flow display 336, and corresponding peak flow
setting button 336a are provided. When peak flow setting button
336a is depressed, value setting knob 300 may be utilized to dial
in the desired peak flow. The peak flow display 336 will,
thereafter, provide a digital display of the currently selected
peak flow.
[0117] The typical range of peak flow settings is 10 to 140 liters
per minute.
[0118] 6. Flow Sensitivity
[0119] A flow sensitivity digital display 338, and corresponding
flow sensitivity setting button 338a are provided. When flow
sensitivity setting button 338a is depressed, value setting knob
300 may be utilized to dial in the desired flow sensitivity
setting. The flow sensitivity setting display 338 will, thereafter,
provide a digital display of the currently selected flow
sensitivity setting.
[0120] The flow sensitivity setting determines the trigger level
for initiation of volume and pressure-controlled assist breaths or
pressure support breaths. The initiation of volitional inspiratory
effort by the patient creates a change in airway flow as determined
by: (turbine bias flow)-(exhalation flow)=patient flow. Triggering
occurs when the patient airway flow exceeds the sensitivity
setting. The typical range of selectable flow sensitivity settings
is from one to ten liters per minute, or off.
[0121] Optionally, a fail safe feature may be incorporated whereby,
if the patients flow demand does not exceed the flow sensitivity
setting, but the airway pressure drops more than 5 cmH.sub.2O below
the set PEEP level, and inspiratory cycle will be initiated and a
breath will be delivered based on current mode and control
settings.
[0122] 7. PEEP/CPAP
[0123] A PEEP/CPAP digital display 340, with corresponding
PEEP/CPAP setting button 340a are provided. When PEEP/CPAP setting
button 340a is depressed, the value setting knob 300 may be
utilized to dial in the desired PEEP/CPAP setting.
[0124] The current PEEP/CPAP setting sets the level of pressure in
the patient circuit that is maintained between the end of
inspiration and the start of the next inspiration. It is also known
as the "baseline" pressure.
[0125] The preferred range of PEEP/CPAP setting is 0 to 50
cmH.sub.2O.
[0126] 8. Pressure Support
[0127] A pressure support digital display 342, and corresponding
pressure support setting button 342a, are provided. When pressure
support setting button 142a is depressed, value setting knob 300
may be utilized to dial in the desired pressure support
setting.
[0128] The pressure support setting determines the inspiratory
patient circuit pressure during a pressure support breath. This
control sets the pressure support level above the baseline setting
established by the PEEP/CPAP setting. The total delivered pressure
equals the PEEP or CPAP value+pressure support.
[0129] The typical range of pressure support settings is from 1 to
60 centimeters of water (cmH.sub.2O), or off.
[0130] 9. FiO.sub.2(%O.sub.2)
[0131] An FiO.sub.2 digital display 348, and corresponding
FiO.sub.2 setting button 348a, are provided. When the FiO.sub.2
setting button 348a is depressed, the value setting knob 300 may be
utilized to dial in the desired fractional percentage of oxygen in
the air/oxygen gas mixture that is delivered to the patient PT and
used for the bias flow. In response to the FiO.sub.2 setting, the
controller 12 will issue control signals to the oxygen blending
apparatus 16 to effect the preset FiO.sub.2.
[0132] The preferred range of setable FiO.sub.2 is between 0.21 and
1.0 (i.e., 21-100 percent oxygen)
[0133] 10. Pressure Control (Optional)
[0134] A pressure control digital display 350, and corresponding
pressure control setting button 350a are provided. When the
pressure control setting button 350a is depressed, the value
setting knob 300 may be utilized to dial in the desired pressure
control value.
[0135] The pressure control setting enables the system 10 to be
utilized for pressure control ventilation, and determines the
inspiratory pressure level during delivery of each pressure control
breath. The pressure control setting sets the pressure level above
any PEEP.
[0136] It is preferable that the range of possible pressure control
settings be from 1 to 100 cmH.sub.2O.
[0137] 11. Inspiratory Time (Optional)
[0138] An optional inspiratory time digital display 352, and
corresponding inspiratory time setting button 352a may be provided.
When the inspiratory time setting button 352a is depressed, the
value setting of 300 may be utilized to dial in the desired
inspiratory time.
[0139] The set inspiratory time is the time period for the
inspiratory phase of a pressure control breath. Thus, this
inspiratory time setting is normally usable for pressure control
ventilation.
[0140] It is preferable that the range of setable inspiratory times
being from 0.3 to 10.0 seconds.
[0141] 12. Additional Displays/Settings
[0142] Additional digital displays 344, 346, 354, 356 and
corresponding setting buttons 344a, 346a, 354a, 356a are provided
to permit the controller 12 to be subsequently programmed or
expanded to receive and display additional control settings beyond
those which have been described hereabove.
[0143] 13. Sigh On/Off
[0144] A sigh on/off button 360 is provided. When sigh on/off
button 360 is depressed, the controller 12 will cause the
ventilator 14 to deliver a sigh breath. A sigh breath is a
volume-controlled, mandatory breath that is usually equal to 1.5
times the current tidal volume setting shown on tidal volume
setting display 332. The sigh breath is delivered according to the
current peak flow setting shown on peak flow setting display 336.
The inspiratory phase of the sigh breath is preferably limited to a
maximum of 5.5 seconds. During a sigh breath, the breath period is
automatically increased by a factor of 1.5. The sigh breath
function is available during all ventilation modes.
[0145] A single depression of the sigh on/off button 348 will cause
the ventilator to deliver a volume-controlled sigh breath once
every 100 breaths or every 7 minutes, which ever comes first. The
sigh breath button 360 includes a visual indicator light 360a which
illuminates when the sigh on/off button 360 is depressed and the
sigh/breath function is active.
[0146] 14. Manual Breath
[0147] A manual breath button 362 is also provided. Upon depression
of the manual breath button 362, the controller 12 will cause the
ventilator 14 to deliver a single volume-controlled or pressure
control breath in accordance with the associated volume and/or
pressure control settings. An indicator light 362a will illuminate
briefly when manual breath button 362 is depressed.
[0148] 15. Remote Alarm (Optional)
[0149] A remote alarm on/off control button 364 is provided to
enable or disable the remote alarm. When the remote alarm on/off
control button 364 is depressed, indicator light 364a will
illuminate. When the remote alarm on/off button 364 is depressed,
the remote alarm will be enabled. When this function is enabled,
alarm conditions will transmit via hard wire or radio frequency
(wireless) to a remote alarm which may be mounted on the outside of
a patients room so as to signal attendants outside of the room,
when an alarm condition exists.
[0150] The specific alarm conditions which may be utilized with the
remote alarm function, are described in greater detail
herebelow.
[0151] 16. Flow Waveform (Optional-Applies to Volume Breaths
Only)
[0152] The controller 12 includes a square flow wave form
activation button 366 and a decelerating taper flow wave form
actuation button 368. When the square flow wave form actuation
button 366 is depressed, indicator light 366a will illuminate, and
the ventilator will deliver inspiratory flow at a constant rate
according to the peak flow setting, as input and shown on peak flow
display 336. When the decelerating paper wave form actuation button
368 is depressed, indicator light 368a will illuminate, and the
ventilator will deliver an inspiratory flow which initially
increases to the peak flow setting, as input and shown on peak flow
display 336, then such inspiratory flow will decelerate to 50
percent of the peak flow setting at the end of the inspiratory
phase.
[0153] 17. Inspiratory Hold (Optional)
[0154] An inspiratory hold actuation button 370 is provided, to
enable the operator to hold the patient at an elevated pressure
following inspiration, so that breath mechanics can be calculated.
The length of the delay period is determined by the period of time
during which the inspiratory hold button 370 remains depressed,
with a maximum limit applied.
[0155] 18. Expiratory Hold (Optional)
[0156] The controller 12 also includes an expiratory hold actuation
button 372, which enables the ventilator to calculate auto PEEP.
During the expiratory hold, the turbine 30 operation is halted and
the exhalation valve 18 remains closed. The difference between the
end expiratory pressure, as measured at the end of the expiratory
hold period, minus the airway pressure reading recorded at the
beginning of the expiratory hold period, will be displayed on
monitor window 384.
[0157] 19. Maximal Inspiratory Pressure/Negative Inspiration Force
(Optional)
[0158] The preferred controller 12 also incorporates a maximal
inspiratory pressure test button 374, to enable the operator to
initiate a maximal inspiratory pressure (MIP) test maneuver. This
maneuver causes the ventilator to stop all flow to or from the
patient. The patient inspiratory effort is then monitored and
displayed as MIP/NIF in the monitor window 384.
[0159] 20. 100% O.sub.2 Suction (Optional)
[0160] Optionally, the controller 12a includes a 100% O.sub.2
actuation button 376 which, when depressed, will cause indicator
light 376a to illuminate and will cause the system 10 to deliver an
FiO.sub.2 of 1.00 (i.e., 100% oxygen) to the patient for a period
of three (3) minutes regardless of the current FiO.sub.2 setting
and/or breath type setting.
[0161] This 100% O.sub.2 feature enables the operator to
selectively deliver 100% oxygen to the patient PT for a three
minute period to hyperoxygenate the patient PT prior to
disconnection of the patient from the ventilator circuit for
purposes of suctioning, or for other clinical reasons.
[0162] 21. Additional Control Actuation Buttons
[0163] An additional control actuation button 378, with indicator
light 378a, is provided to enable the controller 12a to be
subsequently programmed to perform additional control actuation
functions beyond those described hereabove.
[0164] Monitors and Indicators
[0165] 1. AC Power Status Indicator
[0166] An AC power indicator light 304 is provided in the face
panel of the controller 12 to indicate when sufficient AC power is
available and the standby/off switch (not shown) is in the standby
position.
[0167] 2. Internal Battery Status Indicator(s)
[0168] An internal battery status indicator light 308 is provided
on the panel of the controller 12, and will indicate battery charge
level according to predetermined color signals. A separate internal
battery charge indicator light 306 may be provided, and will
indicate charging status according to predetermined color
signals.
[0169] 3. External Battery Status Indicator(s)
[0170] An external battery status indicator light 312 is provided
on the panel of the controller 12, and will indicate battery charge
level according to predetermined color signals. A separate external
battery charge indicator light 310 may be provided, and will
indicate charging status according to predetermined color
signals.
[0171] 4. Airway Pressure Monitor
[0172] The display panel of the controller 12 includes a real time
airway pressure bar graph display 380. A green indicator bar will
appear on the airway pressure bar graph display 380 to indicate the
real time airway pressure at all times. Red indicators will appear
on the airway pressure bar graph to indicate high and low peak
pressure alarm setting, as more fully described herebelow under the
heading "Alarms". An amber colored indicator will appear on the
airway pressure bar graph display 380 to indicate the current
PEEP/CPAP setting, Pressure Support setting and/or Pressure Control
setting. A patient effort indicator light 382 is located near the
airway pressure bar graph display 380, and will illuminate to
indicate the occurrence of a patient-initiated breath, including
all spontaneous, assist or pressure support breaths.
[0173] 5. Digital Monitor Display
[0174] The panel of the controller 12 preferably includes a digital
monitor display 384 and an accompanying monitor select button 386.
The controller 12 is programmed to display various monitored
parameters. Each time the monitor select button 386 is depressed,
the monitored parameters displayed on monitor display 384 will
change. The individual parameters may include: exhaled tidal
volume, i.e., ratio, mean airway pressure, PEEP, peak inspiratory
pressure, total breath rate, total minute ventilation.
[0175] Additionally, a display power saving feature may be
incorporated, whereby the controller 12 will automatically cause
the monitor display 384 to become non-illuminated after a
predetermined display period when the system 10 is operating solely
on internal or external battery power. Each time the monitor select
button 386 is depressed, the display 384 will illuminate for a
predetermined period of time only, and then will become
non-illuminated. This feature will-enable the system 10 to conserve
power when the system 10 is being operated solely on internal or
external battery power.
[0176] Additionally, the controller 12 may be programmed to cause
the monitor display 384 to display a special or different group of
parameters during a specific operator-initiated maneuver. Examples
of special parameter groups which may be displayed during a
specific maneuver include the following:
[0177] Real-time Pressure (at start of and during all
maneuvers)
[0178] Plateau Pressure (Inspiratory Hold)
[0179] Compliance (Inspiratory Hold)
[0180] End Expiratory Pressure (Expiratory Hold)
[0181] Auto PEEP (Expiratory Hold)
[0182] Maximal Inspiratory Pressure (MIP/NIF)
[0183] Alarms and Limits
[0184] The preferred controller 12 may be programmed to received
operator input of one or more limiting parameters, and to provide
audible and/or visual alarm indications when such limiting
parameters have been, or are about to be, exceeded.
[0185] The visual alarm indicators may comprise steady and or
flashing lights which appear on the control panel of the preferred
controller 12a.
[0186] The audible alarm components will preferably comprise
electronic buzzers or beepers which will emit sound discernable by
the human ear for a preselected period (e.g., 3 seconds).
Preferably, the audible portion of any alarm may be volitionally
muted or deactuated by the operator.
[0187] Additionally it is preferable that the controller 12 be
programmed to automatically reset each alarm if the current
ventilation conditions do not fall outside of the preset alarm
limits.
[0188] Examples of specific limiting parameters and alarm limits
which may be programmed into the preferred controller 12, are as
follows:
[0189] 1. High Peak Pressure
[0190] The preferred controller 12 includes, on its face panel, a
high pressure digital display 390 and a corresponding high pressure
alarm limit setting button 390a. When the high pressure alarm limit
setting button 390a is depressed, value setting knob 300 may be
utilized to dial in a desired high pressure alarm limit value. Such
high pressure alarm limit value will then be displayed on high
pressure alarm limit display 390.
[0191] The currently set high pressure alarm limit, as shown on
high pressure alarm limit display 390, will establish the maximum
peak inspiratory pressure for all breath types. When the monitored
airway pressure exceeds the currently set high pressure alarm
limit, audible and visual alarms will be actuated by the controller
12 and the controller will immediately cause the system 10 to cycle
to expiratory mode, thereby allowing the airway pressure to return
to the baseline bias flow level and along the exhalation valve 18
to regulate pressure at any currently-set peep level.
[0192] In order to avoid triggering of the high pressure alarm
during delivery of a sigh breath, the controller 12 will be
programmed to automatically adjust the high pressure alarm limit
value by a factor of 1.5.times. during the deliver of a sigh
breath, provided that such does not result in the high pressure
limit value exceeding 140 cmH.sub.2O. The controller 12 is
preferably programmed not to exceed a high pressure limit setting
of 140 cmH.sub.2O, even during delivery of a sigh breath.
[0193] 2. Low Peak Pressure
[0194] A low peak airway pressure limit display 392, and
corresponding low peak pressure limit setting button 392a, are also
provided. When the low peak pressure limit setting button 392a is
depressed, value setting knob 300 may be utilized to dial in a
desired low peak airway pressure alarm limit value. Such low peak
pressure alarm limit value will then be displayed in the low peak
pressure display 392.
[0195] Audible and/or visual alarms will be activated if the
monitored airway pressure fails to exceed the low peak pressure
alarm limit setting during the inspiratory phase of a
machine-cycled mandatory or assist breath.
[0196] The controller 12 is preferably preprogrammed to
[0197] 5. Spare Alarm Limit Displays and Setting Buttons
[0198] Spare alarm limit displays 396, 398, and corresponding spare
alarm limit setting buttons 396a and 398a are provided, to permit
the controller 12 to be subsequently expanded or programmed to
receive operator input of additional limiting parameters, and to
provide auditory and/or visual alarms when such limiting parameters
have been exceeded.
[0199] 6. Ventilator Inoperative
[0200] A separate ventilator inoperative light indicator 400 is
provided on the face panel of the controller 12. The controller 12
is programmed to cause the ventilator inoperative light to
illuminate when predetermined "ventilatory inoperative" conditions
exist.
[0201] 7. AC Power Low/Fail
[0202] The controller 12 is preferably programmed to activate
visual and/or auditory alarms when an AC power cord is connected to
the system 10 and the voltage received by the system 10 is outside
of a specified operating range. The controller 12 is preferably
also programmed to automatically switch the system 10 to internal
battery power under this condition. The AC power low/fail alarm can
be silenced, and will remain silenced, until such time as the
internal low battery alarm 208 becomes actuated, indicating that
the internal battery has become depleted.
[0203] 8. External/Internal Battery Low/Fail
[0204] The controller 12 may be programmed to actuate a visual and
or auditory alarm when an external or internal battery is in use,
and the battery voltage is outside of an acceptable operating
range.
[0205] 9. O.sub.2 Inlet Pressure
[0206] The controller 12 may be programmed to provide auditory
and/or visual alarms when the oxygen pressure delivered to the
system 10 is above or below predetermined limits.
[0207] 10. Over Pressure Relief Limit
[0208] The system 10 includes a mechanical variable pressure relief
valve 64, to relieve any over pressurization of the patient
circuit.
[0209] The range of setable over pressure relief limit values may
be between 0 to 140 cmH.sub.2O.
[0210] Self Testing and Auto Calibration Functions
[0211] 1. Self Test Function
[0212] The preferred controller 12 may be programmed to perform a
self-testing function each time the ventilator is powered up. Such
self testing function will preferably verify proper functioning of
internal components such as microprocessors, memory, transducers
and pneumatic control circuits. Such self testing function will
also preferably verify that electronic sub-systems are functioning
correctly, and are capable of detecting error conditions relating
to microprocessor electronics.
[0213] Also, during power up, the controller 12 may be programmed
to allow a qualified operator who enters a given key sequence, to
access trouble shooting and calibration information. In accordance
with this feature, the key operator may induce the controller to
display, on the monitor display 384, information such as the
following:
Software Revision
Peak Flow and Pressure Transducer Output Lamp Test/All Displays on
Any Auto Zero and Purge Functions for the Flow Pressure
Transducer
Event Detection Menu Including Previous Status or Fault Codes
Remote Alarm Test and Program; and Data Communications Test and
Program
[0214] Also, the controller 12 may be-programmed to allow a
qualified operator who entered a given key sequence, to access a
user preference and set up menu. Such menu may include a monitory
display 384, of information such as the following:
[0215] System lock, enable or disable;
[0216] Variable Apnea interval;
[0217] Language selection; and
[0218] User verification tests.
[0219] The user preference and set up menu function may also be
accessible during operation of the system 10.
C. A Preferred Rotary Drag Compressor Apparatus
[0220] The portable system 10 ventilator of the present invention
preferably incorporates a rotary drag compressor apparatus 30
comprising a dual-sided, multi-bladed rotor 104 disposed within a
rigid compressor housing 106. An inflow/outflow manifold 108 is
formed integrally with the compressor housing 106, and incorporates
two (2) inflow passageways 112 and two (2) outflow passageways 110
for channeling gas flow into and out of the compressor apparatus
30.
[0221] An electric motor 102, such as a 0.8 peak horsepower, 40
volt D.C. motor, is preferably mounted integrally within the
compressor housing 106. Alternatively, the motor 102 may be encased
or housed in an encasement or housing which is separate from the
compressor housing 106. The motor shaft 114 extends transversely
into, a bore 116 formed in the central hub 118 of rotor 104. As
shown, the bore 116 of the central hub 118 of rotor 104 may include
a rectangular key-way 121 formed on one side thereof and the motor
shaft 114 may include a corresponding elongate rectangular lug
formed thereon. The rectangular lug of the motor shaft 114 inserts
within and frictionally engages the key-way 121 of the rotor hub
118, thereby preventing the motor shaft 114 from rotationally
slipping or turning within the bore 116 of the rotor hub 118. It
will be appreciated however, that various alternative mounting
structures, other than the lug and keyway 121 shown in FIGS. 8-9,
may be utilized to rotatably mount the motor shaft 114 to the rotor
104.
[0222] The rotor hub 118 is preferably formed having a concave
configuration, as shown in FIG. 5. Such concave configuration
serves to impart structural integrity and strength to the rotor
104, without significantly increasing the mass of the rotor 104 as
would result from the formation of additional strengthening ribs or
bosses on the rotor hub 118.
[0223] As shown in FIGS. 5-10, a first annular trough 120 extends
about the periphery of the front side of the rotor 104, and a
second annular trough 122 extends about the periphery of the
backside of the rotor 104.
[0224] A multiplicity of rotor blade-receiving slots 126 are formed
angularly, at evenly spaced intervals about the inner surfaces of
the first 120 and second 122 annular troughs. Rotor blades 128 are
mounted at spaced-apart locations around each annular trough 120,
122 such that the radial peripheral edge 127 of each blade 128 is
inserted into and resides within a corresponding blade receiving
slot 126 and the leading edge 129 of each blade traverses across
the open annular trough 120 or 122, as shown. Each blade 128 is
affixed by adhesive, or other suitable means, to the body of the
rotor 104.
[0225] In the preferred embodiment the blades 128 are located in
axially aligned positions, i.e., non-staggered directly opposite
positions on opposite sides of the rotor 104 so as to promote even
pressure balance and symmetrical weight distribution within the
rotor 104.
[0226] The rotor 104 is rotatably mounted within the compressor
housing 106 such that the first 120 and second 122 annular cavities
are in alignment with the inflow 110 and outflow 112 channels, as
shown.
[0227] In order to optimize the controllability of the rotor 104
velocity, and to minimize the wear or stress on the system drive
components from repeated abrupt starting and stopping of the rotor
104, it is desirable that the overall mass of the rotor 104 be
minimized. Toward this end, the body of the rotor 104 is preferably
constructed of light weight material such as aluminum, and the
individual blades 128 of the rotor 104 are preferably constructed
of light weight material such as glass-filled epoxy. In embodiments
where the body of the rotor 104 is formed of aluminum and the
blades 128 are formed of glass-filled epoxy, a suitable adhesive
such as epoxy may be utilized to bond the radial edges of the
blades 128 within their corresponding blade-receiving slots 126.
Alternatively, it is contemplated to form the rotor and blades
integrally, as by way of a molding process whereby metal (e.g.,
aluminum), polymer or composite materials are molded to form the
blades 128 and rotor 104 as a unitary structure.
[0228] After the rotor blades 128 have been mounted and secured in
their respective blade-receiving slots 126, each individual blade
128 will preferably be disposed at an angle of attack A, relative
to a flat transverse plane TP projected-transversely through the
body of the rotor 104, between the first annular trough 120 on the
front side of the rotor 104, and the second annular trough 122 on
the backside of the rotor 104. The angle A is preferably in the
range of 30-60 degrees and, in the preferred embodiment shown in
FIGS. 8-10 is 55 degrees. Such angle A is selected to provide
optimal flow-generating efficiency of the rotor 104.
[0229] In operation, it is necessary to precisely control the
timing of the acceleration, deceleration, and the rotational speed,
of the rotor 104 in order to generate a prescribed inspiratory
pressure and/or flow rate and/or volume. Although standard
manufacturing tolerances may be maintained when manufacturing the
rotor 104 and other components of the compressor 30 (e.g., the
rotor 104, compressor housing 106, motor 102) each individual
compressor 30 will typically exhibit some individual variation of
flow output as a function of the rotational speed and differential
pressure of that compressor 30. Thus, in order to optimize the
precision with which the inspiratory flow may be controlled, it is
desirable to obtain precise flow and pressure data at various
turbine speeds for each individual compressor 30, and to provide
such characterization data to the controller 12 to enable the
controller 12 to adjust for individual variations in the pressure
and/or flow created by the particular compressor 30 in use. As a
practical matter, this may be accomplished in either of two ways.
One way is to generate discrete flow rate, speed and pressure
measurements for each compressor 30 at the time of manufacture, and
to provide a table of such discreet flow rate, speed and pressure
values to the ventilator controller 12 at the time the particular
compressor 30 is installed. The controller 12 will be
correspondingly programmed to perform the necessary interpolative
mathematical steps to obtain instantaneous flow, speed or pressure
determinations as a function of any two such variables, for the
particular compressor 30. The second way is to experimentally
generate a series of flow, speed and pressure data points over a
range of normal operating rotor speeds, and to subsequently derive
a unique speed vs. flow vs. pressure equation to characterize each
individual compressor 30. Such individual characterization equation
is then programmed into, or otherwise provided to, the controller
12 and the controller 12 is programmed to utilize such equation to
compute precise, instantaneous speed, flow rate and pressure
control signals for controlling the individual compressor 30 in
use. An example of such graphical speed vs. flow rate vs. pressure
data, and a characterization equation derived therefrom, is shown
in FIG. 12.
[0230] Given the current cost of microprocessor technology,
providing a controller 12 which has the capability to receive and
process such a characterization equation as shown in (FIG. 12) for
controlling the compressor 30 would require substantial expense and
size enlargement of the controller 12. Accordingly, given the
present state of the art, it is most desirable to utilize the
former of the two above-described methods--that is, providing a
database of discrete flow, speed and pressure values and
programming of the controller 12 to perform the necessary
mathematical interpolations of the provided data points for
maintaining compressor-specific control of the pressure, flow rate
and/or volume of gas provided in each inspiratory phase at the
ventilation cycle. The experimentally generated database of
discreet flow, speed and pressure valves may be encoded onto an
EPROM or any other suitable database storage device. Such EPROM or
other database storage device may be located on or within the
compressor 30 itself and communicated to the controller 12 via
appropriate circuitry. Alternatively, such EPROM or database
storage device may be installed directly into the controller 12 at
the time the particular compressor 30 is installed within the
ventilator device 14.
[0231] The controlled inspiratory flow generated by the rotary drag
compressor 30, exists from the compressor outlet 34 and through
line 22 to the patient PT. As shown in FIG. 2, an output silencer
60, such as a hollow chamber having a quantity of muffling material
formed therearound, is preferably positioned on inspiratory flow
line 22 to reduce the sound generated by the ventilator 14 during
operation. An inspiration occlusion valve 62 is additionally
preferably mounted on inspiratory flow line 22 to accomplish
operator controlled stoppage of the inspiratory flow as required
during performance of a maximal inspiratory force maneuver.
Additionally, a pressure relief valve 64 is connected to
inspiratory flow line 22 to provide a safeguard against delivering
excessive inspiratory pressure to the patient PT. The pressure
relief valve 64 may be manually set to the desired limit pressure,
by the operator.
[0232] In general, the rotary drag compressor ventilator 14
operates by periodic rotating of the rotor 130 within the
compressor 30 to generate the desired inspiratory gas flow through
line 22. It is desirable that the rotor 130 be accelerated and
decelerated as rapidly as possible. Such rapid
acceleration/deceleration is facilitated by a reduction in inertial
effects as a result of the above-described low mass construction of
the rotor 104. The speed and time of rotation of the rotor 104,
during each inspiratory phase of the ventilator cycle, is
controlled by the controller 12 based on the variables and/or
parameters which have been selected for triggering, limiting and
terminating the inspiratory phase.
[0233] The precise flow, volume or pressure delivered through the
inspiratory line 22 is controlled by the controller based on the
EPROM-stored compressor characterization data received by the
controller, as well as periodic or continuous monitoring of the
rotational speed of the rotor 104 and the change in pressure
(.DELTA..sub.P) between the inlet side 32 and outlet side 34 of the
compressor 30 as monitored by the differential pressure transducer
36.
[0234] In the presently preferred embodiment, the controller 12 is
programmed to deliver breaths by either of two available closed
loop algorithms; volume or pressure.
EXAMPLE
Volume Breaths
[0235] Prior to Volume breath initiation, the controller 12
generates a predefined command waveform of flow vs time. The
waveform is generated using the current Flow, Volume and Waveform
input settings from the front panel. Since the mathematical
integral of flow over time is equal to the volume delivered, the
controller can determine the appropriate inspiratory time. Once a
volume breath has been triggered, the controller uses closed loop
control techniques well known in the art to drive the compressor,
periodically read the compressor differential pressure and
rotational speed, and then calls upon the specific stored
compressor characterization data to arrive at the actual flow rate.
Once actual flow rate is known, it is compared or "fed back" to the
current commanded flow, and a resulting error is derived. The error
is then processed through a control algorithm, and the compressor
speed is adjusted accordingly to deliver the desired flow rate.
[0236] This process is repeated continuously until the inspiration
is complete.
EXAMPLE
Pressure Breaths
[0237] Pressure breaths include several breath types such as
Pressure Support or Pressure Control. In these breath types, the
controller commands the compressor to provide flow as required to
achieve a pressure as input from the front panel. Once a pressure
breath has been triggered, the controller uses closed loop, control
techniques well known in the art to drive the compressor 30 and to
achieve the desired patient airway pressure. The controller
periodically reads the actual airway pressure. Once actual pressure
is known, it is "fed back" and compared to the current commanded
pressure, and a resulting error is derived. The error is then
processed through a control algorithm, and the compressor speed is
adjusted accordingly to deliver the desired pressure. This process
is repeated continuously until the inspiration is complete.
[0238] For both breath types, once the selected inspiratory
termination variable is reached, the controller will signal the
compressor motor 102 to stop or decelerate to a baseline level,
thereby cycling the ventilator in to the expiratory phase.
D. A Preferred Oxygen Blending Apparatus
[0239] When oxygen enrichment of the inspiratory flow is desired,
the controller 12 may be additionally programmed or equipped to
control the operation of the oxygen blending apparatus 16 to mix a
prescribed amount of oxygen with ambient air drawn through air
intake 24, thereby providing an inspiratory flow having a
prescribed oxygen content (FiO.sub.2) between 21% -100%.
[0240] As shown in FIGS. 2 and 3, the preferred oxygen blending
apparatus 16 comprises an air inlet line 24 which opens into a
hollow vessel or accumulator 54.
[0241] Oxygen inlet line 26 is connected to a pressurized source of
oxygen and leads, via a manifold to a series of solenoid valves 52.
Although not by way of limitation, in the preferred embodiment as
shown in FIG. 3, five (5) separate solenoid valves 52a-52e are
utilized. Each such separate solenoid valve 52a-52e has a specific
(usually differing) sized flow restricting orifice formed therein
so that each such solenoid valve 52a-52e will permit differing
amounts of oxygen to pass into accumulator 54, per unit of time
during which each such solenoid valve 52a-52e is maintained in an
open position. The controller 12 is preprogrammed to determine the
specific period(s) of time each solenoid valve 52a-52e must remain
open to provide the necessary amount of oxygen to accumulator 54 to
result in the prescribed oxygen concentration (FiO.sub.2).
[0242] Algorithm for a Preferred Oxygen Blending Apparatus
[0243] The rotational velocity of the rotor 104 and differential
pressure across the inflow/outflow manifold 108 are measured by the
controller 12 and from this data the controller 12 is able to
determine the flow of gas through the compressor 30 from the
accumulator 54. The controller 12 integrates the air flow drawn
through the compressor 30 to determine the accumulated volume of
enriched gas drawn from said accumulator 54. In order to maintain
the flow of gas at the prescribed FiO.sub.2 level, a portion of
this removed volume must be replaced in the accumulator 54 with
pure oxygen.
[0244] The accumulated volume is compared to a predetermined
trigger volume for each of the solenoids 52a-52e, which in the
preferred embodiment, is defined by the equation:
Trigger Volume=(Solenoid Flow*Time*79)/[(FiO.sub.2-21)*2]
[0245] Starting with the smallest, each solenoid that is not
currently open is compared. When the accumulated volume reaches the
trigger volume for a solenoid 52, the controller 12 opens that
solenoid 52 for a period of time allowing oxygen to flow from the
oxygen inlet line 26 through the solenoid 52 and into the
accumulator 54. The controller 12 then adjusts the accumulated
volume appropriately by subtracting a volume, proportional to the
volume of oxygen delivered to the accumulator 54 from the
accumulated volume defined by the equation:
Subtracted Volume=(Solenoid Flow*Time*79)/(FiO.sub.2-21).
[0246] This process is repeated continuously.
[0247] The trigger volume the controller 12 uses to open an
individual solenoid 52a-52e is independent for each solenoid 52 and
is function of the flow capacity of the particular solenoid
52a-52e, the prescribed FiO.sub.2 level, and the amount of time the
solenoid 52 is open. In the preferred embodiment, the amount of
time each solenoid 52 is open is the same for each solenoid 52, but
may vary as a function of oxygen inlet pressure.
EXAMPLE
Delivery of 0.6 FiO.sub.2 Using 4 Solenoids
[0248] In this example, the oxygen blending apparatus has 4
solenoids with flows of 5 lpm, 15 lpm, 40 lpm, and 80 lpm
respectively. The FiO.sub.2 setting is 60%, thus the trigger
volumes for each of the 4 solenoids is 8 ml, 25 ml, 66 ml, and 133
ml respectively. Furthermore a constant oxygen inlet pressure is
assumed resulting in an "on" time of 100 ms for the solenoids, a
constant compressor flow of 60 lpm, and a period of 1 ms. The
following table describes the state of the oxygen blending
algorithm after various iterations:
1 Solenoid Solenoid Solenoid Solenoid Accumulated 1 2 3 4 Time (ms)
Volume (ml) (8 ml) (25 ml) (66 ml) (133 ml) 0 0 off off off off 1 1
off off off off 2 2 off off off off ** 7 7 off off off off 8 0 on
off off off 9 1 on off off off ** 32 24 off off off off 33 0 on on
off off 34 1 on on off off ** 98 65 on on off off 99 0 on on on off
100 1 on on on off ** 107 8 on on on off 108 1 off > on* on on
off *At 108 ms the 8 ml solenoid turned off after having been on
for 100 ms, but since the accumulated volume is now 9 ml the
solenoid is turned on again.
[0249] Thus, by independently operating the four (4) separate
solenoids as shown in the above table, a 0.6 FiO.sub.2 is
consistently delivered through the compressor 30.
E. A Preferred Exhalation Valve and Exhalation Flow Transducer
[0250] Referring generally to FIGS. 11a-11e the preferred
exhalation valve and exhalation flow transducer assembly of the
present invention is depicted. By way of overview, the exhalation
valve 18 comprises a housing which defines an expiratory flow path
therethrough and a valving system for controlling the airway
pressure during the expiratory phase of the ventilation cycle. The
exhalation valve 18 shares numerous structural and functional
attributes with the exhalation valve described in U.S. Pat. No.
5,127,400 (DeVries et al) entitled Ventilator Exhalation Valve,
issued Jul. 7, 1994, the disclosure of which is expressly
incorporated herein by reference.
[0251] In addition, the exhalation valve assembly 18 of the present
invention additionally incorporates an exhalation flow transducer
230 which serves to monitor exhalation flow from the patient and
generates an output signal to the controller 12. The output signal
is then utilized by the controller to determine when patient
exhalation has ceased to thereby initiate inspiratory flow to the
patient. In the preferred embodiment, the exhalation flow
transducer 230 is mounted within the exhalation valve 18 in unique
structure to minimize manufacturing inaccuracies. Further, in the
preferred embodiment, the particular operational characteristics of
the exhalation flow transducer 230 are stored within a memory
device which is then communicated to the controller 12 to insure
accuracy in flow measurements. The exhalation flow transducer 230
of the present invention shares numerous structural and functional
attributes with the flow transducer described in the U.S. Pat. No.
4,993,269, issued to Guillaume et al., entitled Variable Orifice
Flow Sensing Apparatus, issued on Feb. 19, 1991, the disclosure of
which is expressly incorporated herein by reference.
[0252] Referring more particularly to FIGS. 11a through 11e, the
exhalation valve 18 of the present invention is formed having a
housing 200 including an exhalation tubing connector 202 formed at
a first location thereon and an outflow port 204 formed at a second
location thereon. An exhalation gas flow passageway 206 extends
through the interior of the housing 200 such that expiratory gas
may flow from the exhalation tubing connector 202 through the
exhalation passageway 206 within the interior of the exhalation
valve 18 and subsequently passed out of the outflow port 204.
Midway through the expiratory flow passageway 206, there is formed
an annular valve seat 208. The annular valve seat 208 may be
disposed in a plane which is parallel to the plane of the flat
diaphragm 210 or alternatively, as in the embodiment shown, the
annular valve seat 208 may be slightly angled or tapered relative
to the plane in which the flat diaphragm 210 is positioned. Such
angling or tapering of the valve seat 208 facilitates seating of
the diaphragm 210 on the valve seat 208 without flutter or bouncing
of the diaphragm 210. The elastomeric disc or diaphragm 210 is
configured and constructed to initially contact the farthest
extending side of the angled valve seat 208, and to subsequently
settle or conform onto the remainder of the angled valve seat 208,
thereby avoiding the potential for flutter or bouncing which may
occur when the diaphragm 210 seats against a flat non-angled valve
seat 208.
[0253] The disc or diaphragm, 210 is preferably attached to the
surrounding rigid housing 200 by way of an annular flexible
frenulum 212. Frenulum 212 serves to hold the disc or diaphragm 210
in axial alignment with the annular valve seat 208, while
permitting the disc or diaphragm 210 to alternatively move back and
forth between a closed position wherein the diaphragm 210 is firmly
seated against the valve seat 208 (FIG. 11a) and a fully open
position wherein the disc or diaphragm 210 is retracted rearwardly
into the adjacent cavity within the housing 200 thereby providing
an unrestricted flow path 206 through which expiratory gas may
flow.
[0254] A pressure distributing plate 214 is mounted on the backside
of the diaphragm 210. A hollow actuation shaft 216 is mounted
within the housing 200 and is axially reciprocal back and forth to
control the position of the diaphragm 210 relative the valve seat
208. A bulbous tip member 218 is mounted on the distal end of a
hollow actuation shaft 216. A corresponding pressure distribution
plate 214 is mounted on the back of the diaphragm 210. Forward
movement of the actuation shaft 216 causes the bulbous tip member
218 to exert forward pressure against the plate 214 thereby forcing
the diaphragm 210 toward its closed position. When the actuation
shaft 216 is in a fully forward position, the diaphragm 210 will be
held in firm abutment against the annular valve seat 208 thereby
terminating flow through the passage 206. Conversely when the
actuation shaft 216 is retracted, the diaphragm 210 moves away from
the valve seat 208 thereby allowing flow through the passageway 206
thereby allowing flow through the passageway 206.
[0255] The movement of the shaft 216 is controlled by way of an
electrical induction coil 220 and spider bobbin 222 arrangement. In
the preferred embodiment, the electrical induction coil 220 is
formed without having an internal support structure typically
utilized in induction coils so as to minimize inertial concerns. In
this regard, the coil 220 is typically formed by winding upon a
mandrel and subsequently maintained in this wound configuration by
way of application of a suitable binder or varnish. Additionally,
in the preferred embodiment, the bobbin 222 is preferably formed
having a cross-beam construction, as shown in FIG. 11b, to decrease
the mass of the bobbin 222 while maintaining its structural
integrity. Similarly, the shaft 216 is preferably formed from a
hollow stainless steel material so as to be relatively strong yet
light weight enough for minimizing inertial concerns.
[0256] As shown, the bobbin 222 is affixed to the distal end of the
induction coil 220 and the shaft 216 extends through an aperture
formed in the center of the bobbin and is frictionally or otherwise
affixed to the bobbin such that the shaft 216 will move back and
forth in accordance with the bobbin 222 and coil 220. As the
current passing into the induction coil 220 increases, the coil 220
will translate rearwardly into the coil receiving space 226 about
the magnet thereby moving the shaft 216 and blunt tip member 218 in
the rearward direction and allowing the diaphragm 210 to move in an
open position away from the valve seat 208 of the expiratory flow
path 206. With the diaphragm 210 in such open position, expiratory
flow from the patient PT may pass through the expiratory flow
pathway 206 and out the expiratory port 204.
[0257] Conversely, when the expiratory flow has decreased or
terminated, the current into the induction coil may change
direction, thereby causing the induction coil to translate
forwardly. Such forward translation of the induction coil 220 will
drive the bobbin 222, shaft 216, and bulbous tip member 218 in a
forward direction, such that the bulbous tip member 218 will press
against the flow distributing plate 214 on the backside of the
diaphragm 210 causing the diaphragm to seat against the valve seat
208. With the diaphragm 210 seated against the valve seat 208, the
inspiratory phase of the ventilator cycle may begin and ambient air
will be prevented from aspirating or backflowing into the patient
circuit through the exhalation port 204.
[0258] In the preferred embodiment, a elastomeric boot 217 or dust
barrier is mounted about the distal portion of the hollow actuation
shaft 216, and is configured and constructed to permit the shaft
216 to freely move back and forth between its fully extended closed
position and a fully retracted open position while preventing dust
or moisture from seeping or passing into the induction coil
220.
[0259] As best shown in FIG. 11, FIGS. 11a and 11c, the housing of
the exhalation valve 18 includes a frontal portion formed by the
housing segments 200b, 200c, and 200d. An airway pressure passage
241 is provided within the housing portion 200b, which enables the
pressure within the exhalation passageway 206 to be communicated to
an airway pressure tubing connector 233. Airway pressure tubing
connector 233 is connected via tubing to an airway pressure
transducer 68 (shown in FIG. 2) which monitors airway pressure and
outputs a signal to the controller 12. Based upon desired operating
conditions, the controller 12, in response of receipt of the
pressure signal from pressure transducer 68 increases or decreases
the voltage applied to the coil 220 to maintain desired pressure
within the exhalation air passage 206. As will be recognized, such
monitoring of the airway pressure is continuous during operation of
the ventilator cycle.
[0260] As previously mentioned, the exhalation flow transducer 230
of the present invention is preferably disposed with the exhalation
valve housing and serves to monitor exhalation flow from the
patient PT. More particular, the exhalation flow transducer 230 of
the present invention preferably incorporates a feedback control
system for providing real time monitoring of the patient's actual
expiratory flow rate. As best shown in FIGS. 11a and 11c, the
expiratory flow transducer 230 of the present invention is
incorporated within the exhalation flow path 206 within housing
segment 200b. The flow transducer 230 is preferably formed from a
flat sheet of flexible material having a cut out region 406 formed
therein. A peripheral portion 408 of the flat sheet exists outside
of the cut out region 406 and flapper portion 231 is defined within
the cut out region 406. Frame members 410 and 412 preferably formed
of a polymer material, are mounted on opposite sides of the flat
sheet so as to exert inward clamping pressure on the peripheral
portion 408 of the flat sheet. The flapper portion 231 of the flat
sheet is thus held in its desired transverse position within the
open central aperture 14a and 14b of the transducer assembly, and
such flapper portion 231 is thus capable of flexing downstream in
response to exhalation flow.
[0261] To minimize the inducement of stresses within the flow
transducer assembly 230, a frame member 411 is preferably
positioned in abutting juxtaposition to the outboard surface of at
least one of the frame members 410, 412. In the preferred
embodiment shown in FIG. 11c, the frame member 411 is positioned in
abutment with the upper frame member 410. Such frame member 411
comprises a metal frame portion 413 and includes an elastomeric
cushioning gasket or washer 415 disposed on the lower side thereof.
A central aperture 14c is formed in the frame member 411, such
aperture 14c being of the same configuration, and in axial
alignment with central apertures 14a, 14b of the upper and lower
frame members 410, 412.
[0262] Upper and lower abutment shoulders 418a, 418b, are formed
within the exhalation valve housing 200 to frictionally engage and
hold the flow transducer assembly 230 in its desired operative
position. When so inserted, the upper engagement shoulder 418a will
abut against the upper surface of the frame member 411, and the
lower abutment shoulder 418b will abut against the lower surface of
the lower frame member 412, thereby exerting the desired inward
compressive force on the flow transducer assembly 230. As will be
recognized, the inclusion of the cushioning washer 415 serves to
evenly distribute clamping pressure about the peripheral portion
408, thereby minimizing the creation of localized stress within the
flow transducer 230.
[0263] When the transducer assembly 230 is operatively positioned
between the upper and lower abutment shoulders 418a, 418b, an
upstream pressure port 232 will be located upstream of the flapper
231, and a downstream pressure port 234 will be located downstream
of the flapper 231. By such arrangement, pressures may be
concurrently measured through upstream pressure port 232 and
downstream pressure port 234 to determine the difference in
pressures upstream and downstream of the flapper 231.
[0264] As expiratory gas flow passes outwardly, through the outlet
port of the exhalation valve 18, the flapper portion 231 of the
flow transducer 230 will deflect or move allowing such expiratory
gas flow to pass thereacross, but also creating a moderate flow
restriction. The flow restriction created by the flow transducer
230 results in a pressure differential being developed across the
flow transducer 230. Such pressure differential may be monitored by
pressure ports 232 and 234 disposed on opposite side of the flow
transducer 230 (as shown in FIG. 11a) which pressure ports are in
flow communication by internal passages formed within the housing
segment 200c, 200b and 200a to tubing connections 240 and 235. A
manifold insert 201 may be mounted on the upstream pressure port
232 such that the manifold insert 201 protrudes into the expiratory
flowpath 206, upstream of the flapper 231. A plurality of inlet
apertures 201a, preferably four in number are formed around the
outer sidewall of the manifold insert 201, and communicate through
a common central passageway with the upstream pressure port 232,
thereby facilitating accurate measurement of the pressure within
the expiratory flowpath 206 at that location.
[0265] An exhalation differential pressure transducer 70 (shown in
FIG. 2) may be located within the housing or enclosure of the
ventilator 10. The exhalation differential pressure transducer 70
is connected by way of tubing to the first and third pressure port
tubing connectors 240 and 235 so as to continuously measure and
provide the controller 12 with the difference between pressure
upstream (P1) and pressure downstream (P2) of the flow transducer
230. The difference in pressure determined by the exhalation
differential pressure transducer 70 is communicated to the
controller, and the controller is operatively programmed to
calculate the actual flow rate at which expiratory gas is exiting
the flow channel 206. As will be recognized, the exhalation flow
rate may be utilized by the controller 12 for differing purposes
such as triggering of initiation of the next inspiratory cycle.
[0266] Although the particular formation and mounting structure
utilized for the exhalation flow transducer 230 provides
exceptional accuracy in most situations, the applicant has found
that in certain circumstances, it is desirable to eliminate any
inaccuracies caused by manufacturing and assembly tolerances. As
such, in the preferred embodiment, the specific operational
characteristics of each exhalation flow transducer 230, i.e.,
pressure differential for specific flow rates are measured for
calibration purposes and stored on a storage medium contained
within the exhalation valve housing 18. In the preferred embodiment
this specific characterization and calibration information is
encoded on a radio frequency transponder 203 of the type
commercially available under the product name Tiris, manufactured
by Texas Instruments, of Austin, Tex. The radio-frequency
transponder 203 and its associated transmitter/receiver antenna
203a may be mounted within the exhalation valve housing 200 as
shown in FIG. 11c. Additionally, a radio frequency
transmitter/receiver is positioned within the ventilator system 10,
such that upon command of the controller 12, the calibration and
characterization data contained within the transponder 203 is
transmitted via radio frequency to the receiver and stored within
the controller 12. Subsequently, the controller 12 utilizes such
stored calibration and characterization data to specifically
determine expiratory flow rate based upon pressure differential
values generated by the differential pressure transducer 70.
F. A Preferred Auto Calibration Circuit
[0267] In the preferred embodiment, the ventilator device 14 of the
ventilator system 10 of the present invention incorporates an auto
calibration circuit for periodic rezeroing of the system to avoid
errors in the tidal volume or inspiratory flow delivered by the
drag compressor 30.
[0268] In particular, as shown in FIG. 2 the preferred auto
calibration circuit comprises the following components:
[0269] a) a first auto-zero valve 74 on the line between the inlet
32 of the compressor 30 and the differential pressure transducer
36;
[0270] b) a second auto-zero valve 76 on the line between the first
pressure port of the exhalation valve 18 and the first pressure
(P1) side of the exhalation differential pressure transducer
70;
[0271] c) a third auto-zero valve 80 on the line between the second
pressure (P2) port 234 of the exhalation valve 18 and the second
pressure (P2) side of the exhalation differential pressure
transducer 70;
[0272] d) a fourth auto-zero valve 78 on the line between the
outlet port 34 and the differential pressure transducer 36; and
[0273] e) and a fifth auto-zero valve 72 on the line between the
airway pressure port 241 and the airway pressure transducer 68.
[0274] Each of the auto-zero valves 72, 74, 76, 78, 80 is connected
to the controller 12 such that, at selected time intervals during
the ventilatory cycle, the controller 12 may signal the auto-zero
valves 72, 74, 76, 78, 80 to open to atmospheric pressure. While
the auto-zero valve 72, 74, 76, 78, 80 are open to atmospheric
pressure, the controller 12 may re-zero each of the transducers 36,
68, 70 to which the respective auto-zero valve 72, 74, 76, 80 are
connected. Such periodic re-zeroing of the pressure transducers 36,
68 and 70 will correct any baseline (zero) drift which has occurred
during operation.
Ventilator Operation
[0275] With the structure defined, the basic operation of the
ventilator system 10 of the present invention may be described. As
will be recognized, the particular ventilatory mode selected by a
technician may be input to the controller 12 via the input controls
upon, the display 380. Additionally, the technician must attach the
inspiratory and exhalation tubing circuit to the patient PT as
illustrated in FIG. 1.
[0276] Prior to initiation of patient ventilation, the controller
12 initiates its auto calibration circuit and system check to
insure that all system parameters are within operational
specifications. Subsequently, inspiration is initiated wherein the
controller 12 rapidly accelerates the drag compressor 30. During
such acceleration, air is drawn through the filter 50, accumulator
54 and supplied to the patient PT, via line 22. During such
inspiratory phase, the controller 12 monitors the pressure drop
across the compressor 30, via pressure transducer 36, and the
rotational speed of the rotor 104. This data is then converted to
flow by the controller 12 via the turbine characterization table to
insure that the proper flow and volume of inspiratory gas is
delivered to the patient PT. Additionally, during such inspiratory
phase, the exhalation valve 18 is maintained in a closed position.
In those applications where oxygen blending is desired, the
controller 12 additionally opens selected ones of the solenoid
valve 52a, 52b, 52c, 52d and 52e, in timed sequence to deliver a
desired volume of oxygen to the accumulator 54, which is
subsequently delivered to the patient PT during inspiratory flow
conditions.
[0277] When inspiratory flow is desired to be terminated, the
controller 12 rapidly stops or decelerates the drag compressor 30
to a basal rotational speed, and the patient is free to exhale
through exhalation line 66 and through the exhalation valve 18.
Depending upon desired ventilation mode operation, the controller
12 monitors the exhalation pressure, via pressure transducer 68
connected to the airway passage and adjusts the position of the
valve relative the valve seat within the exhalation valve 18 to
maintain desired airway pressures. Simultaneously, the controller
12 monitors the pressure differential existing across the
exhalation flow transducer 230 via exhalation pressure transducer
70 to compute exhaled flow. This exhaled flow is used to compute
exhaled volume and to determine a patient trigger. When a breath is
called for either through a machine or patient trigger, the
controller initiates a subsequent inspiratory flow cycle with
subsequent operation of the ventilator system 10 being repeated
between inspiratory and exhalation cycles.
[0278] Those skilled in the art will recognize that differing
ventilation modes, such as intermittent mandatory ventilation
(IMV), synchronized intermittent mandatory ventilation (SMIV)
controlled mechanical ventilation (CMV) and assist control
ventilation (A/C), are all available modes of operation on the
ventilator 10 of the present invention. Further those skilled in
the art will recognize that by proper selection of control inputs
to the ventilator 10, all modern breath types utilized in clinical
practice, may be selected, such as machine cycled mandatory breath,
machine cycled assist breath, patient cycled supported breath,
patient cycled spontaneous breath, volume controlled mandatory
breaths, volume controlled assist breaths, pressure controlled
breaths, pressure support breaths, sigh breaths, proportional
assist ventilation and volume assured pressure support.
* * * * *